Showing papers on "Aldehyde dehydrogenase published in 1999"

Isolation of primitive human hematopoietic progenitors on the basis of aldehyde dehydrogenase activity.

Abstract: Because hematopoietic stem cells are rich in aldehyde dehydrogenase (ALDH) activity, we developed a fluorescent substrate for ALDH, termed BODIPY aminoacetaldehyde (BAAA), and tested its potential for isolating primitive human hematopoietic cells. A population of cells with low orthogonal light scattering and bright fluorescence intensity (SSCloALDHbr cells) could be readily fractionated from human umbilical cord blood cells costained with BAAA and the multidrug-resistance inhibitor verapamil. The SSCloALDHbr population was depleted of lineage-committed cells, 40–90% pure for CD34+CD38lo/− cells, and enriched 50- to 100-fold for primitive hematopoietic progenitors detected in short- and long-term culture analyses. Together, these observations indicate that fractionating human hematopoietic stem cells on the basis of ALDH activity using BAAA is an effective method for isolating primitive human hematopoietic progenitors. This technique may be useful for isolating stem cells from other tissues as well.

Eukaryotic aldehyde dehydrogenase (ALDH) genes: human polymorphisms, and recommended nomenclature based on divergent evolution and chromosomal mapping.

Abstract: As currently being performed with an increasing number of superfamilies, a standardized gene nomenclature system is proposed here, based on divergent evolution, using multiple alignment analysis of all 86 eukaryotic aldehyde dehydrogenase (ALDH) amino-acid sequences known at this time. The ALDHs represent a superfamily of NAD(P)(+)-dependent enzymes having similar primary structures that oxidize a wide spectrum of endogenous and exogenous aliphatic and aromatic aldehydes. To date, a total of 54 animal, 15 plant, 14 yeast, and three fungal ALDH genes or cDNAs have been sequenced. These ALDHs can be divided into a total of 18 families (comprising 37 subfamilies), and all nonhuman ALDH genes are named here after the established human ALDH genes, when possible. An ALDH protein from one gene family is defined as having approximately or = 60% amino-acid identity and are expected to be located at the same subchromosomal site. For naming each gene, it is proposed that the root symbol 'ALDH' denoting 'aldehyde dehydrogenase' be followed by an Arabic number representing the family and, when needed, a letter designating the subfamily and an Arabic number denoting the individual gene within the subfamily; all letters are capitalized in all mammals except mouse and fruit fly, e.g. 'human ALDH3A1 (mouse, Drosophila Aldh3a1).' It is suggested that the Human Gene Nomenclature Guidelines (http://++www.gene.ucl.ac.uk/nomenclature/guidelines.h tml) be used for all species other than mouse and Drosophila. Following these guidelines, the gene is italicized, whereas the corresponding cDNA, mRNA, protein or enzyme activity is written with upper-case letters and without italics, e.g. 'human, mouse or Drosophila ALDH3A1 cDNA, mRNA, or activity'. If an orthologous gene between species cannot be identified with certainty, sequential naming of these genes will be carried out in chronological order as they are reported to us. In addition, 20 human ALDH variant alleles that have been reported to date are listed herein and are recommended to be given numbers (or a number plus a capital letter) following an asterisk (e.g. 'ALDH3A2*2, ALDH2*4C'). It is anticipated that this eukaryotic ALDH gene nomenclature system will be extended to include bacterial genes within the next 2 years and that this nomenclature system will require updating on a regular basis; an ALDH Web site has been established for this purpose (http://++www.uchsc.edu/sp./sp./alcdbase/a ldhcov.html) and will serve as a medium for interaction amongst colleagues in this field.

A proposal for nomenclature of aldehyde dehydrogenases in Saccharomyces cerevisiae and characterization of the stress-inducible ALD2 and ALD3 genes.

Abstract: The complete sequencing of the genome of Saccharomyces cerevisiae indicated that this organism contains five genes encoding aldehyde dehydrogenases. YOR374w and YER073w correspond to the mitochondrial isoforms and we propose as gene names ALD4 and ALD5, respectively. YPL061w has been described as the cytoplasmic constitutive isoform and named ALD6. We characterize here the tandem-repeated ORFs YMR170c and YMR169c as the cytoplasmic stress-inducible isoforms, with gene names ALD2 and ALD3, respectively. The expression of ALD2 and ALD3 is dependent on the general-stress transcription factors Msn2,4 but independent of the HOG MAP kinase pathway. ALD3 is induced by a variety of stresses, including osmotic shock, heat shock, glucose exhaustion, oxidative stress and drugs. ALD2 is only induced by osmotic stress and glucose exhaustion. A double null mutant, ald2 ald3, exhibited unchanged sensitivity to any of the above stresses. The only phenotype detected in this mutant was a reduced growth rate in ethanol medium as compared to the wild type.

The ald gene, encoding a coenzyme A-acylating aldehyde dehydrogenase, distinguishes Clostridium beijerinckii and two other solvent-producing clostridia from Clostridium acetobutylicum.

Abstract: The coenzyme A (CoA)-acylating aldehyde dehydrogenase (ALDH) catalyzes a key reaction in the acetone- and butanol (solvent)-producing clostridia It reduces acetyl-CoA and butyryl-CoA to the corresponding aldehydes, which are then reduced by alcohol dehydrogenase (ADH) to form ethanol and 1-butanol The ALDH of Clostridium beijerinckii NRRL B593 was purified It had no ADH activity, was NAD(H) specific, and was more active with butyraldehyde than with acetaldehyde The N-terminal amino acid sequence of the purified ALDH was determined The open reading frame preceding the ctfA gene (encoding a subunit of the solvent-forming CoA transferase) of C beijerinckii NRRL B593 was identified as the structural gene (ald) for the ALDH The ald gene encodes a polypeptide of 468 amino acid residues with a calculated M(r) of 51, 353 The position of the ald gene in C beijerinckii NRRL B593 corresponded to that of the aad/adhE gene (encoding an aldehyde-alcohol dehydrogenase) of Clostridium acetobutylicum ATCC 824 and DSM 792 In Southern analyses, a probe derived from the C acetobutylicum aad/adhE gene did not hybridize to restriction fragments of the genomic DNAs of C beijerinckii and two other species of solvent-producing clostridia In contrast, a probe derived from the C beijerinckii ald gene hybridized to restriction fragments of the genomic DNA of three solvent-producing species but not to those of C acetobutylicum, indicating a key difference among the solvent-producing clostridia The amino acid sequence of the ALDH of C beijerinckii NRRL B593 was most similar (41% identity) to those of the eutE gene products (CoA-acylating ALDHs) of Salmonella typhimurium and Escherichia coli, whereas it was about 26% identical to the ALDH domain of the aldehyde-alcohol dehydrogenases of C acetobutylicum, E coli, Lactococcus lactis, and amitochondriate protozoa The predicted secondary structure of the C beijerinckii ALDH suggests the presence of an atypical Rossmann fold for NAD(+) binding A comparison of the proposed catalytic pockets of the CoA-dependent and CoA-independent ALDHs identified 6 amino acids that may contribute to interaction with CoA

The structure of retinal dehydrogenase type II at 2.7 A resolution: implications for retinal specificity.

Abstract: Retinoic acid, a hormonally active form of vitamin A, is produced in vivo in a two step process: retinol is oxidized to retinal and retinal is oxidized to retinoic acid. Retinal dehydrogenase type II (RalDH2) catalyzes this last step in the production of retinoic acid in the early embryo, possibly producing this putative morphogen to initiate pattern formation. The enzyme is also found in the adult animal, where it is expressed in the testis, lung, and brain among other tissues. The crystal structure of retinal dehydrogenase type II cocrystallized with nicotinamide adenine dinucleotide (NAD) has been determined at 2.7 A resolution. The structure was solved by molecular replacement using the crystal structure of a mitochondrial aldehyde dehydrogenase (ALDH2) as a model. Unlike what has been described for the structures of two aldehyde dehydrogenases involved in the metabolism of acetaldehyde, the substrate access channel is not a preformed cavity into which acetaldehyde can readily diffuse. Retinal dehydr...

Detoxifying activity in pig livers and hepatocytes intended for xenotherapy

Abstract: Background Both livers and hepatocytes from pigs have been proposed for the treatment of end-stage liver diseases, as an alternative to allogeneic liver transplants. However, little is known of the capability of porcine hepatocytes to fulfill the biotransformation pathways of toxic compounds, including those released from livers in acute failure. We have studied the activity and expression of detoxifying enzymes in porcine livers and in cultured hepatocytes and their induction by phenobarbital. Methods Cytochromes P450 (CYP) 1A, 2B, and 3A and GST-like activities were tested with the following specific substrates: 7-ethoxyresorufin, 7-pentoxyresorufin, nifedipine, testosterone, 1-chloro-2,4-dinitrobenzene, 1,2-dichloro-4-nitrobenzene, and ethacrinic acid. CYP 1A1/2-, 2B1/2-, 2E1- and 3A4-related and GSTalpha proteins were analyzed by Western blotting and CYP 1A1/2, 2B1/2, 2C6, 2E1, and 3A4, aldehyde dehydrogenase, epoxide hydrolase, and GSTalpha-like RNA by Northern blotting. Results Enzymatic activities reflecting the expression of CYP 1A-, CYP 2B-, CYP 2E1-, and CYP 3A-like genes, that is, ethoxyresorufin-O-deethylase, pentoxyresorufin-O-deethylase, nifedipine oxidase and testosterone 6beta-hydroxylase, and chlorzoxazone 6-hydroxylase, were identified in pig livers. CYP 1A and CYP 2E1, GSTalpha-like proteins, CYP 1A, 2C, and 2E, epoxide hydrolase, aldehyde dehydrogenase, and GST like RNA were expressed in vivo and in vitro. CYP 2B and CYP 3A RNA and proteins, and their associated activities were induced by phenobarbital. Conclusions Porcine hepatocytes express the most important biotransformation enzymes and their corresponding activities and RNA. Thus, livers and hepatocytes from pigs can detoxify a large spectrum of exogenous and endogenous compounds, which makes them a convenient substitute for allogeneic transplants for patients with liver failure.

Differences in the roles of conserved glutamic acid residues in the active site of human class 3 and class 2 aldehyde dehydrogenases.

Abstract: Although the three-dimensional structure of the dimeric class 3 rat aldehyde dehydrogenase has recently been published (Liu ZJ et al., 1997, Nature Struct Biol 4:317-326), few mechanistic studies have been conducted on this isoenzyme. We have characterized the enzymatic properties of recombinant class 3 human stomach aldehyde dehydrogenase, which is very similar in amino acid sequence to the class 3 rat aldehyde dehydrogenase. We have determined that the rate-limiting step for the human class 3 isozyme is hydride transfer rather than deacylation as observed for the human liver class 2 mitochondrial enzyme. No enhancement of NADH fluorescence was observed upon binding to the class 3 enzyme, while fluorescence enhancement of NADH has been previously observed upon binding to the class 2 isoenzyme. It was also observed that binding of the NAD cofactor inhibited the esterase activity of the class 3 enzyme while activating the esterase activity of the class 2 enzyme. Site-directed mutagenesis of two conserved glutamic acid residues (209 and 333) to glutamine residues indicated that, unlike in the class 2 enzyme, Glu333 served as the general base in the catalytic reaction and E209Q had only marginal effects on enzyme activity, thus confirming the proposed mechanism (Hempel J et al., 1999, Adv Exp Med Biol 436:53-59). Together, these data suggest that even though the subunit structures and active site residues of the isozymes are similar, the enzymes have very distinct properties besides their oligomeric state (dimer vs. tetramer) and substrate specificity.

Materials and methods for the alteration of enzyme and acetyl CoA levels in plants

Abstract: The present invention provides nucleic acid and amino acid sequences of acetyl CoA synthetase (ACS), plastidic pyruvate dehydrogenase (pPDH), ATP citrate lyase (ACL), Arabidopsis pyruvate decarboxylase (PDC), and Arabidopsis aldehyde dehydrogenase (ALDH), specifically ALDH-2 and ALDH-4. The present invention also provides a recombinant vector comprising a nucleic acid sequence encoding one of the aforementioned enzymes, an antisense sequence thereto or a ribozyme therefor, a cell transformed with such a vector, antibodies to the enzymes, a plant cell, a plant tissue, a plant organ or a plant in which the level of an enzyme has been altered, and a method of producing such a plant cell, plant tissue, plant organ or plant. Desirably, alteration of the level of enzyme results in an alteration of the level of acetyl CoA in the plant cell, plant tissue, plant organ or plant. In addition, the present invention provides a recombinant vector comprising an antisense sequence of a nucleic acid sequence encoding pyruvate decarboxylase (PDC), the E1α subunit of pPDH, the E1β subunit of pPDH, the E2 subunit of pPDH, mitochondrial pyruvate dehydrogenase (mtPDH) or aldehyde dehydrogenase (ALDH) or a ribozyme that can cleave an RNA molecule encoding PDC, E1α pPDH, E1β pPDH, E2 pPDH, mtPDH or ALDH.

An A/G polymorphism in the promoter of mitochondrial aldehyde dehydrogenase (ALDH2): effects of the sequence variant on transcription factor binding and promoter strength.

Abstract: Introduction: The strong protective effect of the ALDH2*2 mutation on risk of alcoholism suggests that other mutations that reduce mitochondrial aldehyde dehydrogenase (ALDH) activity in the liver might also deter drinking. This study describes a polymorphic locus found in the promoter of the ALDH2 gene that affects expression of reporter constructs. Method: Polymerase chain reaction (PCR)-based sequencing was used to search for polymorphisms. The ability of the promoter variants to bind transcription factors apolipoprotein A regulatory protein 1 (ARP-1) and chicken ovalbumin upstream promoter-transcription factor (COUP-TF) was tested in gel retardation assays using in vitro synthesized transcription factors. The variant promoters were tested for transcriptional activity using a heterologous promoter system and transient transfection assays. Result: A common polymorphism (A or G) in the human ALDH2 promoter region was found at -361 base pair (bp) from the translation start site. This polymorphism was found at different frequencies in African Americans, Caucasians, and Asians. The polymorphism occurs adjacent to the core binding motif for the transcription factors COUP-TF and ARP-1. Competition and binding affinity determinations did not show differences in the ability of these two sequences to bind the factors. Reporter genes containing these elements upstream of a basal thymidine kinase promoter had similar activity when transfected into a fibroblast (CV-1) cell line. However, the reporter containing the G allele was more active than that containing the A allele in hepatoma (H4IIEC3) cells. Conclusions: The -361 bp A/G polymorphism is common in all racial groups tested. The G allele was more active than the A allele in a transfection assay. The basis for this difference is not known. If the differences in activity of the promoter constructs were paralleled by differences in ALDH2 enzyme activity in the liver, this polymorphism could affect risk of alcoholism.

Aldehyde Dehydrogenase Gene Superfamily

Abstract: Aldehydehydrogenases (ALDHs) represent a group of NAD(P)+-dependent enzymes, which e similar primary structures and oxidize a wide spectrum of endogenous and exnous aldehydes (Lindahl, 1992; Vasiliou et al., 1995). Several ALDHs display broad strate specificities, oxidizing a variety of both aliphatic and aromatic aldehydes, whereather forms possess narrower substrate preferences. Based on substrate specificities, ALDH emes are broadly categorized as:a. semialdehyde dehydrogenases, including hydroxymuconic semialdehyde dehydrogenase (E.C. 1.2.1.32), Escherichia coli (EC 1.2.1.16) and mammalian (EC 1.2.1.24) succinate-semialdehyde dehydrogenase, glutamate semi aldehyde dehydrogenase (E.C. 1.2.1.41), aspartate semialdehyde dehydrogenase (E.C. 1.2.1.11), 2-amino-adipate-6-semialdehyde dehydrogenase (E.C. 1.2.1.31) and metylmalonate- semialdehyde dehydrogenase (E.C. 1.2.1.27), b. nonspecific ALDHs (E.C.I.2.1.3), c. other ALDHs including betaine dehydrogenase (E.C. 1.2.1.8), non phosphorylating glyceraldehyde 3-phosphatedehydrogenase (E.C. 1.2.1.9), phenylacetaldehyde dehydrogenase (EC 1.2.1.39), lactaldehyde dehydrogenase (EC 1.2.1.22), and d. ALDike proteins which represent certain other protein sequences, containing either complete or almost complete ALDH sequences. These include the 10-formyltetrahydrofolate dehydrogenase (E.C. 1.5.1.6), Δ1-pyrroline-5-carboxylate dehydrogenase (EC 1.5.1.12), antiquitin, a human 56-kDa androgen-binding protein, and the crystallins..

Inhibition of human aldehyde dehydrogenase 1 by the 4-hydroxycyclophosphamide degradation product acrolein.

Abstract: In a previous study, we observed that the elimination clearance of 4-hydroxycyclophosphamide (HCY) in patients receiving cyclophosphamide (CY) 60 mg/kg/day by 1-h i.v. infusion for 2 consecutive days decreased from day 1 to day 2 due to an apparent decrease in human aldehyde dehydrogenase 1 (ALDH1) activity. Here, the mechanism for the decrease in ALDH1 activity after CY administration was investigated. In human liver cytosol incubations, HCY inhibited ALDH activity mainly through its degradation product acrolein, whereas carboxyethylphosphoramide mustard inhibited ALDH activity only at supraclinical concentrations. Other CY metabolites evaluated, phosphoramide mustard and chloroacetaldehyde, did not inhibit ALDH. The inhibition of ALDH1 activity by acrolein in incubations with human erythrocyte ALDH1 was competitive with a Ki of 0.646 microM. The inhibition was independent of preincubation time and reversible by dialysis. The percentage of inhibition of ALDH1 activity in vivo by acrolein in patients receiving CY was calculated based on the in vitro Ki of acrolein, the in vitro Km of HCY, and the in vivo peak blood concentrations of HCY and acrolein. The calculations indicated that the activity of ALDH1 was inhibited by 85, 88, and 91% on days 1, 2, and 3 (24 h after the dose on day 2) of CY administration, respectively. The increase in ALDH1 inhibition with time is consistent with the decrease in HCY elimination clearance and the increase in HCY area under the plasma concentration time curve with time.

Involvement of mitochondrial aldehyde dehydrogenase ALD5 in maintenance of the mitochondrial electron transport chain in Saccharomyces cerevisiae.

Abstract: The physiological role of mitochondrial aldehyde dehydrogenase (ALD5) was investigated by analysis of the ald5 mutant (AKD321) in Saccharomyces cerevisiae. K+-activated ALDH activity of the ald5 mutant was about 80% of the wild-type in the mitochondrial fraction, while the respiratory activity of the ald5 mutant was greatly reduced. Cytochrome content was also reduced in the ald5 mutant. Enzymatic analysis revealed that the alcohol dehydrogenase activity of the ald5 mutant was higher than that of the wild-type, while glycerol 3-phosphate dehydrogenase activity was the same in the two strains. Ethanol as a carbon source or addition of 1 M NaCl with glucose as the carbon source in the growth medium increased β-galactosidase activity from an ALD5-lacZ fusion. Overexpression of another mitochondrial ALDH gene (ALD7) had no effect on increasing respiratory function of the ald5 mutant, but showed improved growth on ethanol. These observations show that mitochondrial ALD5 plays a role in regulation or biosynthesis of electron transport chain components.

Dose-dependent inhibition of cell proliferation induced by lipid peroxidation products in rat hepatoma cells after enrichment with arachidonic acid.

Abstract: Polyunsaturated fatty acids (PUFA) are important constituents of membrane phospholipids, whose levels are decreased in some tumor cells. This deficiency may cause alterations in signal transduction and an interruption of normal cellular events. The enrichment of tumor cells with PUFA may stimulate or inhibit tumor growth, probably depending on the type of PUFA and the cellular concentration of aldehydes derived from restored lipid peroxidation. We examined the effect of several doses of prooxidant on the growth of hepatoma cells with different aldehyde dehydrogenase activities, enriched with arachidonic acid. Two doses of prooxidant were sufficient to reduce growth of hepatoma cells with low aldehyde dehydrogenase activity, whereas three doses were necessary for those with high enzyme activity. In both cases, lipid peroxidation products blocked the cells in the S phase.

Retinoic Acid Synthesis and Metabolism

Abstract: It is well known from the early literature that liver alcohol dehydrogenase catalyzes the oxidation of retinol to retinal (Blaner and Olson 1994). Similarly, it was established from early work that several members of the aldehyde dehydrogenase family of enzymes are able to catalyze irreversibly the oxidation of retinal to retinoic acid (Blaner and Olson 1994). Thus,it has long been understood that retinoic acid synthesis from its precursor retinol involves a two step oxidation that resembles the oxidation of ethanol to acetic acid.

Diethylcarbamoylating/Nitroxylating Agents as Dual Action Inhibitors of Aldehyde Dehydrogenase: A Disulfiram−Cyanamide Merger

Abstract: Benzenesulfohydroxamic acid (Piloty's acid) was functionalized on the hydroxyl group with the N,N-diethylcarbamoyl group, and the hydroxylamine nitrogen was substituted with acetyl (1a), pivaloyl (1b), benzoyl (1c), and ethoxycarbonyl (1d) groups. Only compound 1d inhibited yeast aldehyde dehydrogenase (AlDH) in vitro (IC50 169 μM). When administered to rats, 1d significantly raised blood acetaldehyde levels following ethanol challenge, thus serving as a diethylcarbamoylating/nitroxylating, dual action inhibitor of AlDH in vivo. A more potent dual action agent was N-(N,N-diethylcarbamoyl)-O-methylbenzenesulfohydroxamic acid (5c), which was postulated to release diethylcarbamoylnitroxyl (9), a highly potent diethylcarbamoylating/nitroxylating agent, following metabolic O-demethylation in vivo. The dual action inhibition of AlDH exhibited by 1d, and especially 9, constitutes a merger of the mechanism of action of the alcohol deterrent agents, disulfiram and cyanamide.

Mechanism of inhibition of rat liver class 2 ALDH by 4-hydroxynonenal.

Abstract: Lipid oxidation is a pathological process that results in the peroxidation of cellular membrane lipids ultimately giving rise to a number of reactive, cytotoxic, aldehydic products (Esterbauer et al, 1991). 4-hydroxy-2-trans-nonenal (4-HNE) malondialdehyde (MDA), the most abundant aldehydes produced during lipid peroxidation, have a relatively long half-life and are capable of diffusing to distant sites within the cell of origin or into adjacent cells. 4-HNE can produce a variety of adverse cellular effects which have b summarized in detail elsewhere (Schauer et al, 1990) and include the inhibition of various enzymes (Vander Jagt et al, 1997). The ability of certain biogenic aldehydes to produce diverse biological and cytotoxic effects can be attributed to their α, β-unsaturated configuration that gives the compounds strong electrophilic properties (Esterbauer et al, 1991).us, investigators attribute these adverse effects to the formation of aldehyde ad- ducts h cellular protein nucleophiles through covalent alkylation of sulfhydryl, primary amino, and histidyl groups of proteins (Hartley et al, 1997; Uchida and Stadtman, 1993).

Human Corneal and Lens Aldehyde Dehydrogenases

Abstract: Aldehyde dehydrogenases (ALDHs) are now recognised as a complex gene family., which includes a group of NAD-dependent ALDH (EC 1.2.1.3) isozymes. Seven human ALDHs have been reported, of which ALDH1, 2, 3, 5, 6, and 7 (Hsu et al, 1994), and a related enzyme, γ-amino butyraldehyde dehydrogenase (GABADH) (Kurys et al, 1993), have been thus far cloned and sequenced (Hsu et al., 1994). Sequence analysis verifies that these are closely related enzymes, and optimised alignments show that 62 amino acids are conserved, including the catalytically significant Gly-245, Gly-250, Glu-268 and Cys-302 (Hsu et al., 1994). Human ALDHs 1, 2 and 3 have been further classified according to their genetic identity as Class 1(ALDH1, liver cytosolic), Class 2 (ALDH2, liver mitochondrial) and Class 3(ALDH3, stomach cytosolic) isozymes. In addition, a gene locus designated ALDHx, which shares 85% homology with Class 2 ALDH, has also been reported (Hsu and Chang, 1991).

Reduced aldehyde dehydrogenase levels in the brain of patients with Down syndrome.

Abstract: Aldehyde dehydrogenase (ALDH) is a key enzyme in fructose, acetaldehyde and oxalate metabolism and represents a major detoxification system for reactive carbonyls and aldehydes. In the brain, ALDH exerts a major function in the metabolism of biogenic aldehydes, norepinephrine, dopamine and diamines and γ-aminobutyric acid. Subtractive hybridization studies in Down Syndrome (DS) fetal brain showed that mRNA for ALDH are downregulated. Here we studied the protein levels in the brain of adult patients. The proteins from five brain regions of 9 aged patients with DS and 9 controls were analyzed by two-dimensional (2-D) gel electrophoresis and identified by matrix-assisted laser desorption ionization mass spectrometry. ALDH levels were reduced in the brain regions of at least half of the patients with Down Syndrome, as compared to controls. The decreased ALDH levels in the DS brain may result in accumulation of aldehydes which can lead to the formation of plaques and tangles reflecting abnormally cross-linked, insoluble and modified proteins, found in aged DS brain. Furthermore, we constructed a 2-Dmap including approximately 120 identified human brain proteins.

A low-molecular-mass protein from Methylococcus capsulatus (Bath) is responsible for the regulation of formaldehyde dehydrogenase activity in vitro

Abstract: Summary: An 8·6 kDa protein, which the authors call a modifin, has been purified from Methylococcus capsulatus (Bath) and has been shown to alter the substrate specificity and kinetics of NAD+-linked formaldehyde dehydrogenase (FDH) isolated from the same organism. Purification methods for both the modifin and FDH are presented which reliably produced pure protein for further analysis. Analysis of the molecular mass and N-terminal sequence of both FDH and the modifin indicate that they are unique proteins and show no similarity to alcohol or aldehyde dehydrogenase enzymes isolated from methylotrophic bacteria. Substrate specificity studies demonstrated that FDH oxidized formaldehyde exclusively in the presence of the modifin; a diverse range of aldehydes and alcohols were oxidized by FDH in the absence of the modifin. No formaldehyde oxidation was detected in the absence of the modifin. Attempts to replace the modifin with glutathione or high concentrations of methanol to stimulate formaldehyde oxidation failed. With acetaldehyde as substrate, FDH showed standard Michaelis-Menten kinetics; interaction of FDH reaction to sigmoidal. Kinetic analysis during turnover experiments indicated that the FDH may be associated with bound formaldehyde following enzyme isolation and that NAD may also be associated with the enzyme but in a form that is less tightly bound than found with the methanol dehydrogenase from Bacillus methanolicus. Data are presented which indicate that the modifin may play an important role in regulating formaldehyde concentration in vivo.