The goal of this review is to present a comprehensive survey of the many intriguing facets of creatine (Cr) and creatinine metabolism, encompassing the pathways and regulation of Cr biosynthesis an...

http://www.afboard.com/library/creatinemetabolism.pdf

Creatine and Creatinine Metabolism

An overview of the recent developments in polylactide (PLA) research.

Mercury is one of the most hazardous contaminants that may be present in the aquatic environment, but its ecological and toxicological effects are strongly dependent on the chemical species present. Species distribution and transformation processes in natural aquatic systems are controlled by various physical, chemical, and biological factors. Depending on the prevailing environmental conditions, inorganic mercury species may be converted to many times more toxic methylated forms such as methylmercury, a potent neurotoxin that is readily accumulated by aquatic biota. Despite a considerable amount of literature on the subject, the behavior of mercury and many of the transformation and distribution mechanisms operating in the natural aquatic environment are still poorly understood. This review examines the current state of knowledge on the physicochemical behavior of mercury in the aquatic environment, and in particular the environmental factors influencing its transformation into highly toxic methylated forms.

Mercury in the Aquatic Environment: A Review of Factors Affecting Methylation

Environmental, economic, and safety challenges have provoked packaging scientists and producers to partially substitute petrochemical-based polymers with biodegradable ones. The general purpose of this review is to introduce poly-lactic acid (PLA), a compostable, biodegradable thermoplastic made from renewable sources. PLA properties and modifications via different methods, like using modifiers, blending, copolymerizing, and physical treatments, are mentioned; these are rarely discussed together in other reviews. Industrial processing methods for producing different PLA films, wrappings, laminates, containers (bottles and cups), are presented. The capabilities of PLA for being a strong active packaging material in different areas requiring antimicrobial and antioxidant characteristics are discussed. Consequently, applications of nanomaterials in combination with PLA structures for creating new PLA nanocomposites with greater abilities are also covered. These approaches may modify PLA weaknesses for some food packaging applications. Nanotechnology approaches are being broadened in food science, especially in packaging material science with high performances and low concentrations and prices, so this category of nano-research is estimated to be revolutionary in food packaging science in the near future. The linkage of a 100% bio-originated material and nanomaterials opens new windows for becoming independent, primarily, of petrochemical-based polymers and, secondarily, for answering environmental and health concerns will undoubtedly be growing with time.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1541-4337.2010.00126.x

Poly-Lactic Acid: Production, Applications, Nanocomposites, and Release Studies.

Bacterial resistance to inorganic and organic mercury compounds (HgR) is one of the most widely observed phenotypes in eubacteria. Loci conferring HgR in Gram-positive or Gram-negative bacteria typically have at minimum a mercuric reductase enzyme (MerA) that reduces reactive ionic Hg(II) to volatile, relatively inert, monoatomic Hg(0) vapor and a membrane-bound protein (MerT) for uptake of Hg(II) arranged in an operon under control of MerR, a novel metal-responsive regulator. Many HgR loci encode an additional enzyme, MerB, that degrades organomercurials by protonolysis, and one or more additional proteins apparently involved in transport. Genes conferring HgR occur on chromosomes, plasmids, and transposons and their operon arrangements can be quite diverse, frequently involving duplications of the above noted structural genes, several of which are modular themselves. How this very mobile and plastic suite of proteins protects host cells from this pervasive toxic metal, what roles it has in the biogeochemical cycling of Hg, and how it has been employed in ameliorating environmental contamination are the subjects of this review.

Bacterial mercury resistance from atoms to ecosystems

Thirty-one isomers of polychlorinated biphenyl (PCB) were examined for biodegradability by two species of Alcaligenes and Acinetobacter. The following relationships between chlorine substitution and biodegradability of PCBs were observed. (i) Degradation decreased as chlorine substitution increased. PCB isomers containing more than four chlorines were less susceptible to degradation. (ii) PCBs containing two chlorines on either the ortho position of a single ring (i.e., 2,6-) or on both rings (i.e., 2,2′-) showed very poor degradability. (iii) PCBs containing all chlorine atoms on only a single ring were generally degraded faster than when the same number of chlorines were substituted on both rings. (iv) Preferential ring fission of the molecules occurred with nonchlorinated or lesser chlorinated rings. (v) The formation and accumulation of a yellow intermediate was always observed in 4′-chloro-substituted PCBs. (vi) Significant differences between the two organisms with respect to degradability were not observed except for 2,4,6-trichlorobiphenyl.

Effect of Chlorine Substitution on the Biodegradability of Polychlorinated Biphenyls

Microbial characteristics of two bacterial strains, of Alcaligenes and Acinetobacter capable of assimilating biphenyl and 4-chlorobiphenyl as a sole source of carbon have been studied with respect to polychlorinated biphenyl degradation A variety of aromatic compounds were examined for the growth and O2 uptake of the organisms It was observed that these organisms were able to adsorb 14C-2, 5, 2′-trichlorobiphenyl onto the cell surface in a short time and then gradually metabolized the adsorped one The metabolites were moved into aqueous layer from the cells, Several spots including a yellow colored intermediate, ie meta cleavage product, and 2, 5-dichlorobenzoic acid as main products were detected on a thin-layer chromatography and subsequent autoradiography However, neither incorporation of 14C-metabolites into the cell constituents nor 14CO2 evolution was observed

/pdf/alcaligenes-and-acinetobacter-strains-capable-of-degrading-x6yz2yyfdm.pdf

Alcaligenes and Acinetobacter Strains Capable of Degrading Polychlorinated Biphenyls

Two genes encoding haloacetate dehalogenases, H-1 and H-2, are closely linked on a plasmid from Moraxella sp. strain B. H-1 predominantly acts on fluoroacetate, but H-2 does not. To elucidate the molecular relationship between the two enzymes, we compared their structural genes. Two restriction fragments of the plasmid DNA were subcloned on M13 phages and their nucleotide sequences were determined. The sequence of each fragment contained an open reading frame that was identified as the structural gene for each of the two dehalogenases on the basis of the following criteria; N-terminal amino acid sequence, amino acid composition, and molecular mass. The genes for H-1 and H-2, designated dehH1 and dehH2, respectively, had different sizes (885 bp and 675 bp) and G + C contents (58.3% and 53.4%). Sequence analysis revealed no homology between the two genes. We concluded that the dehalogenases H-1 and H-2 have no enzyme-evolutionary relationship. The deduced amino acid sequence of the dehH1 gene showed significant similarity to those of three hydrolases of Pseudomonas putida and a haloalkane dehalogenase of Xanthobacter autotrophicus. The dehH2 coding region was sandwiched between two repeated sequences about 1.8 kb long, which might play a part in the frequent spontaneous deletion of dehH2 from the plasmid.

Lack of homology between two haloacetate dehalogenase genes encoded on a plasmid from Moraxella sp. strain B.

Pseudomonas 0–3 strain which was isolated from soil can grow on polyvinyl alcohol (PVA) as a sole carbon source. When 0.5 per cent of PVA (500, 1500 or 2000) was employed as the carbon source in the culture medium, PVA was almost completely lost from the culture fluid after a week and the concentration of total organic carbon measured by a TOC analyzer decreased from the initial value of about 2700 ppm to 250~300 ppm after 7~10 days culture. This bacterium was found to produce and secrete an inducible enzyme which degrade PVA. The way by which this enzyme degrades PVA was examined and the results were obtained which suggested that PVA was broken down oxidatively in a way of endowise splitting. However, the mechanism of PVA degradation has not been clarified yet. The optimum pH and temperature for enzyme activity were examined and they were 7.5~8.5 and 35~45°C, respectively. Morphological and biological characteristics of this bacterium were examined and it was similar to a strain of Pseudomonas boreopolis.

Some Characteristics of Pseudomonas O-3 which Utilizes Polyvinyl Alcohol

Fifty-six commercially available proteases were tested for polylactide-degrading activity. Little or no activity was found in acid and neutral proteases, while some alkaline proteases formed appreciable amounts of lactic acid from polylactide. These polylactide-degrading proteases were derived from Bacillus species and had catalytic activity even under neutral, as well as alkaline, conditions. Savinase (Novo Nordisk) degraded polylactide the fastest among the enzymes tested and its specific activity corresponded to about one-half of proteinase K. Polylactide-degrading activity was not always present in the enzymes that affected keratin, while polylactide-degrading proteases commonly hydrolyzed keratin. A significant correlation was observed between degrading activities of polylactide and keratin in alkaline proteases.

Kenzo Tonomura

Papers

Effect of Chlorine Substitution on the Biodegradability of Polychlorinated Biphenyls

Alcaligenes and Acinetobacter Strains Capable of Degrading Polychlorinated Biphenyls

Lack of homology between two haloacetate dehalogenase genes encoded on a plasmid from Moraxella sp. strain B.

Some Characteristics of Pseudomonas O-3 which Utilizes Polyvinyl Alcohol

Degradation of Polylactide by Commercial Proteases