Showing papers on "Tyrosine published in 1980"
TL;DR: It is inferred that pp60src is a novel protein kinase and that the modification of proteins via the phosphorylation of tyrosine is essential to the malignant transformation of cells by Rous sarcoma virus.
Abstract: The protein kinase activity associated with pp60src, the transforming protein of Rous sarcoma virus, was found to phosphorylate tyrosine when assayed in an immunoprecipitate. Despite the fact that a protein kinase with this activity has not been described before, several observations suggest that pp60src also phosphorylates tyrosine in vivo. First, chicken cells transformed by Rous sarcoma virus contain as much as 8-fold more phosphotyrosine than do uninfected cells. Second, phosphotyrosine is present in pp60src itself, at one of the two sites of phosphorylation. Third, phosphotyrosine is present in the 50,000-dalton phosphoprotein that coprecipitates with pp60src extracted from transformed chicken cells. We infer from these observations that pp60src is a novel protein kinase and that the modification of proteins via the phosphorylation of tyrosine is essential to the malignant transformation of cells by Rous sarcoma virus. pp60sarc, the closely related cellular homologue of viral pp60src, is present in all vertebrate cells. This normal cellular protein, obtained from both chicken and human cells, also phosphorylated tyrosine when assayed in an immunoprecipitate. This is additional evidence of the functional similarity of these structurally related proteins and demonstrates that all uninfected vertebrate cells contain at least one protein kinase that phosphorylates tyrosine.
2,061 citations
TL;DR: Epidermal growth factor-enhanced protein kinase activity in plasma membrane preparations of A-431 human epidermoid carcinoma cells was shown to involve the phosphorylation of tyrosine residues, which was detected in both endogenous membrane proteins and in histone when added as an exogenous protein substrate.
1,096 citations
TL;DR: Increased phosphorylation of tyrosine is neither a universal mechanism of transformation nor an inevitable secondary cellular response to transformation, suggesting strongly that the modification of one or more cellular polypeptides by way of pp60 src is critical for cellular transformation by Rous sarcoma virus.
485 citations
TL;DR: The Abelson murine leukaemia virus protein (P120) can become phosphorylated in vitro by [γ-32P]ATP and is linked to P120 at tyrosine, a linkage not previously reported for a phosphorylation reaction.
Abstract: The Abelson murine leukaemia virus protein (P120) can become phosphorylated in vitro by [γ-32P]ATP. The protein has been purified from cell membranes to the point that in specific conditions virtually all of the incorporated 32P is in P120. The reaction is stimulated by Mn2+ and Mg2+ but not Ca2+ and is very rapid even at 0 °C. The phosphate is linked to P120 at tyrosine, a linkage not previously reported for a phosphorylation reaction. Phosphorylation may be involved in the transforming activity of viruses that cause leukaemia as well as sarcomas.
474 citations
TL;DR: The possibility that plant cells may undergo Ca2+-dependent regulatory events that are mediated by calmodulin in a manner similar to those found in animals is discussed.
Abstract: A protein activator of plant NAD kinase has been extracted from plant sources (peanuts and peas), purified to homogeneity, characterized, and identified as calmodulin. A comparison of the properties of calmodulin isolated from either plant or animal sources shows that they are strikingly similar proteins. The similarities include molecular weight, Stokes radii, amino acid composition, Ca2+-dependent enhancement of tyrosine fluorescence, Ca2+-dependent interaction with troponin I, equal abilities to activate cyclic nucleotide phosphodiesterase, Ca2+-dependent inhibition of calmodulin action by the phenothiazine drugs, and electrophoretic mobility. We discuss the possibility that plant cells may undergo Ca2+-dependent regulatory events that are mediated by calmodulin in a manner similar to those found in animals.
196 citations
TL;DR: In this paper, Lineweaver-Burk analysis of crude or purified rat pheochromocytoma tyrosine hydroxylase activity, as a function of pterin cofactor concentration, in the absence of ATP, Mg2+, and protein kinase catalytic subunit, yields a curvilinear relationship which can be resolved into two lines, suggesting two enzyme forms with different affinities for pterins cofactor.
Abstract: Data demonstrating the direct phosphorylation of tyrosine hydroxylase [tyrosine 3-monooxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] purified from rat pheochromocytoma by ATP, Mg2+ and cyclic AMP-dependent protein kinase catalytic subunit are presented. The incorporation of phosphate is highly correlated with the activation of the hydroxylase when either the time of preincubation or the amount of protein kinase subunit is varied. The rate of phosphorylation of tyrosine hydroylase compares favorably with that of H1 histone, a known substrate of protein kinase. Lineweaver-Burk analysis of crude or purified rat pheochromocytoma tyrosine hydroxylase activity, as a function of pterin cofactor concentration, in the absence of ATP, Mg2+, and protein kinase catalytic subunit, yields a curvilinear relationship which can be resolved into two lines, suggesting two enzyme forms with different affinities for pterin cofactor. A fraction of the hydroxylase present in the tumor exists in the activated state, presumably due to the presence of ATP and endogenous protein kinase activity. When the solubl enzyme is activated by cyclic AMP, ATP, Mg2+, and protein kinase, virtually all of the enzyme is converted to the low Km state. We conclude that tyrosine hydroxylase is a substrate of cyclic AMP-dependent protein kinase in vitro and, presumably, in vivo.
184 citations
TL;DR: Protein degradation in isolated rat hepatocytes, as measured by the release of [14C]valine from pre-labelled protein, is partly inhibited by a physiologically balanced mixture of amino acids, indicating that the amino acids act exclusively upon the lysosomal pathway of protein degradation.
177 citations
TL;DR: Observations indicate that P140 is the transforming protein of FSV and that protein phosphorylation at tyrosine residues is involved in transformation by this virus.
138 citations
TL;DR: The Y73 strain of avian sarcoma virus recently isolated in Japan is defective in replication and is associated with subgroup A leukosis virus (YAV).
Abstract: The Y73 strain of avian sarcoma virus recently isolated in Japan is defective in replication and is associated with subgroup A leukosis virus (YAV). The virus caused sarcoma but not acute leukosis when inoculated into chickens. Studies on the viral RNA showed that a 26S RNA, etimated to be 4.8 kilobases long, was Y73 viral RNA carrying a transforming gene. The 26S RNA has sequences in common with the RNA of an avian leukosis virus but no homology with the src gene sequence of avian sarcoma virus (ASV). Thus, Y73 has a unique sarcoma-inducing gene. A phosphorylated polyprotein of 90,000 daltons (p90) was immunoprecipitated from extracts of Y73-transformed chicken embryo cells by a variety of antisera reacting with gag gene products. When a bacteria-bound immunocomplex containing the p90 protein was incubated with [gamma-32P]ATP, the Y73-specific p90 and the IgG heavy chain were phosphorylated by a p90-associated protein kinase. The amino acid phosphorylated in vitro was exclusively tyrosine in both cases, whereas p90 phosphorylated in vivo contained phosphoserine as a major phospho amino acid with traces of phosphotyrosine and phosphothreoine.
137 citations
TL;DR: Manducin appears to be a storage form for amino acids sequestered during larval life to be used for construction of the adult animal.
124 citations
TL;DR: There is a unique amino acid pattern associated with operative trauma which is relatively unaffected by hypocaloric, intravenous nutrition, which is almost identical to those seen after colectomy or accidental injury.
Abstract: This study examines the effect of three different hypocaloric diets on the patterns of muscle and plasma amino acids in patients undergoing total hip replacement. Group I (seven patients) received 90 g/day of glucose, Group II (seven patients) received 70 g/day of amino acids, Group III (eight patients) received both 90 g of glucose and 70 grams of amino acids per day. Utilizing the percutaneous biopsy technique of Bergstrom, free amino acid patterns in muscle and plasma were analyzed pre- and postoperatively (day 4). The postoperative pattern of amino acids was characterized by elevated levels in muscle and plasma of the branched chain amino acids, phenylalanine, tyrosine and methionine. There was a marked decrease in muscle glutamine and smaller decreases in the basic amino acids in both muscle and plasma. Muscle:plasma concentration ratios increased for the neutral amino acids, decreased for glutamine and the basic amino acids and were unchanged for the acidic amino acids. The patterns seen after hip replacement are almost identical to those seen after colectomy or accidental injury. There was little effect of diet on amino acid concentrations in muscle. In plasma, concentrations of leucine, isoleucine, valine and proline were higher in Group II in the absence of glucose intake, than in the other groups. Lysine was lower in Group I with no amino acid intake than in the other groups. Thus, there is a unique amino acid pattern associated with operative trauma which is relatively unaffected by hypocaloric, intravenous nutrition.
TL;DR: In this article, the electrochemical properties of amino acids containing no sulfur atoms have been investigated using stationary or rotating solid electrodes such as Au and vitreous carbon, and the first of the second electrochemical oxidation pathway can be favored.
TL;DR: Statistical analysis of the data indicates that at least three different amino acid transport systems are operative in erythrocytes: a system for anionic amino acids (aspartate and glutamate), which concentrates these amino acids intracellularly, reaching high ERYthrocyte/plasma (E/P) concentration ratios; a concentrating system of A type, transporting serine, glycine and alanine and maintaining E/P ratios less than two; and a system of L
TL;DR: With several proteins shown that electrons can be transferred intramolecularly from tyrosine to electron-deficient tryptophan units, it seems likely that the electron transfer proceeds directly between the aromatic groups, while they are maintained at a distance from each other.
TL;DR: The tyrosyl-tRNA synthetases appear to have adequate amino acid selection by simple preferential binding of the correct substrate by using samples of phenylalanine freed from tyrosine by either chemical or enzymic scavenging procedures.
Abstract: The specificity of the tyrosyl-tRNA synthetases from Escherichia coli and bacillus stearothermophilus for tyrosine compared with phenylalanine has been determined by using samples of phenylalanine which have been scrupulously freed from tyrosine by either chemical or enzymic scavenging procedures. Both kinetic measurements and product analyses give a value of 1 x 10(5)-2 x 10(5) for the preferential activation of tyrosine. Combined with the known ratio of phenylalanine to tyrosine in rapidly growing E. coli, an error rate of about approximately 5/10(4) is calculated for the misactivation of phenylalanine. Since we find no evidence for an editing mechanism and this error rate is similar to observed rates in protein synthesis, the tyrosyl-tRNA synthetases appear to have adequate amino acid selection by simple preferential binding of the correct substrate. The incremental binding energy of the phenolic hydroxyl group of tyrosine is approximately 7 kcal/mol, a value presumed close to the maximum possible because of the evolutionary pressure on tyrosyl-tRNA synthetases for maximum specificity. A summary of high incremental binding energies determined from experiments on aminoacyl-tRNA synthetase is presented.
TL;DR: These dehydrogenase characterizations are highly reliable for the keying of a given species to one of the five rRNA homology groups and further document the validity and utility of the approach of comparative enzymology and allostery for classification of microorganisms.
Abstract: Enzymes of tyrosine biosynthesis (prephenate dehydrogenase and arogenate dehydrogenase) were characterized in 90 species currently classified within the genera Pseudomonas, Xanthomonas, and Alcaligenes. Variation in cofactor specificity and regulatory properties of the dehydrogenase proteins allowed the separation of five groups. Taxa defined by enzymological patterning corresponded strikingly with the five ribosomal ribonucleic acid (rRNA) homology groups established via rRNA-deoxyribonucleic acid hybridization. rRNA homology groups I, IV, and V all lack activity for arogenate/nicotinamide adenine dinucleotide phosphate (NADP) dehydrogenase and separated on this criterion from groups II and III, which have the activity. Group II species possess arogenate dehydrogenase enzyme (reactive with either NAD or NADP) sensitive to feedback inhibition by tyrosine, thereby separating from group III species whose corresponding enzyme was totally insensitive to feedback inhibition. The presence of prephenate/NADP dehydrogenase in group IV defined its separation from groups I and V, which lack this enzyme activity. Group I species possess an arogenate/NAD dehydrogenase that was highly sensitive to inhibition by tyrosine and a prephenate/NAD dehydrogenase of relative insensitivity to tyrosine inhibition. The opposite pattern of sensitivity/insensitivity was seen in group V species. These dehydrogenase characterizations are highly reliable for the keying of a given species to one of the five rRNA homology groups. If necessary, other confirmatory assays can be included using other aromatic pathway enzymes. These results further document the validity and utility of the approach of comparative enzymology and allostery for classification of microorganisms.
TL;DR: The plant enzyme was studied by administration of (αS)-[α-3H,U-14C]tyrosine to intact Papaver somniferum plants followed by isolation of the resultant papaverine, which retained no tritium; morphine was also isolated to act as an internal standard.
Abstract: Tyrosine is proved to be decarboxylated with retention of configuration by three aromatic amino-acid decarboxylases of bacterial, mammalian, and plant origin by experiments based on the synthesis of (αS)-[α-3H]tyrosine and the (αR)- and (αS)-isomers of [α-3H1]tyramine. Incubation of the labelled tyramines with the diamine oxidase from pea seedlings and the monoamine oxidase from rat liver shows that the former enzyme removes Hsi and the latter HRe. These amine oxidases are used to assay the chirality of the [α-3H1]tyramines produced by incubation of suitably labelled tyrosines in tritiated water or in unlabelled water with the partially purified decarboxylases from Streptococcus faecalis and hog kidney. The plant enzyme was studied by administration of (αS)-[α-3H,U-14C]tyrosine to intact Papaver somniferum plants followed by isolation of the resultant papaverine, which retained no tritium; morphine was also isolated to act as an internal standard.
TL;DR: A tubulin-tyrosine ligase was purified from porcine brains using DEAE-cellulose chromatography, Sepharose-sebacic acid hydrazide-ATP affinity chromatography and SepharOSE-tubulin affinity Chromatography to catalyze the tyrosination of the alpha subunit of tubulin in vitro.
Abstract: A tubulin-tyrosine ligase was purified from porcine brains using DEAE-cellulose chromatography, Sepharose-sebacic acid hydrazide-ATP affinity chromatography and Sepharose-tubulin affinity chromatography. The purified enzyme migrated as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and its molecular weight was estimated to be 46,000. The apparent molecular weight was 37,000 on a high speed liquid chromatograph equipped with gel filtration columns. The pH optimum for the activity was around 8 and a second peak was observed at around 6.5 8.5 microM ATP or 30 microM tyrosine gave half-maximal activity. The purified enzyme catalyzed the tyrosination of the alpha subunit of tubulin in vitro.
TL;DR: Although in most respects the melanin produced from tyrosine by mushroom and mammalian tyrosinses are similar, the control mechanisms involved in the expression of melanin formation in these organisms must differ greatly.
TL;DR: In this paper, the major high molecular weight proteins synthesized and secreted by murine C1300 neuroblastoma cells as fibronectin, laminin and type IV procollagen were also found to be deposited in pericellular matrix form.
Abstract: Murine neuroblastoma cells have been widely used as a model system for neuronal cells as they can be induced to differentiate in culture by various stimuli, such as dibutyryl cyclic AMP (dbcAMP)1, prostaglandin2, and serum starvation3. The cells respond with assembly of microtubules, leading to neurite outgrowth4,5, with increased activity of neuronal-specific enzymes, tyrosine hydroxvlase, choline acetyltransferase and acetylcholine-esterase6,7, and synthesis of neurotransmitters8. The differentiated cells lose tumorigenicity9. Cell-to-substratum adhesion is evidently crucial for neurone extension in vitro10. Neurite outgrowth is induced by treatments that increase cell-to-substratum adhesion in some neuronal cell cultures11,12. We have now identified the major high molecular weight proteins synthesized and secreted by murine C1300 neuroblastoma cells as fibronectin, laminin and type IV procollagen, of which the latter two were also found to be deposited in pericellular matrix form.
01 Jan 1980
TL;DR: This chapter discusses aromatic amino acid biosynthesis and its regulation and describes the shikimate pathway enzymes, which exist in the chloroplast and also in the cytoplasm.
Abstract: Publisher Summary This chapter discusses aromatic amino acid biosynthesis and its regulation. The multibranched shikimic acid pathway provides the precursors for synthesis of the three common protein amino acids—phenylalanine, tyrosine, and tryptophan—in both microorganisms and higher plants. Secondary metabolites such as alkaloids, coumarins, flavonoids, lignin precursors, indole derivatives, and other phenolic compounds arise from this pathway. The pathway of aromatic amino acid biosynthesis is common to all organisms capable of de novo synthesis. Shikimate kinase enzyme catalyzes the phosphorylation of shikimate to yield shikimate 3-phosphate. Tryptophan biosynthesis diverges from the common precursors of phenylalanine and tyrosine with the conversion of chorismate to anthranilate. The formation of anthranilate proceeds with an elimination of the enolpyruvyl side chain of chorismate accompanied by a glutamine donated amidotransfer. Regulation of biosynthesis in the multibranched shikimic acid pathway relies heavily on feedback mechanisms. The shikimate pathway enzymes exist in the chloroplast and also in the cytoplasm.
TL;DR: These studies show that serine, glutamine, tyrosine or leucine residues can replace the glutamic acid residue found in the wild-type coat protein at position 2 and seem to inhibit processing since pre-coat protein accumulates in the infected cells.
TL;DR: There is a fraction of tubulin that is unable to accept tyrosine, and this non-aminoacylatable tubulin fraction increases with the age of the animal so that in the 120-day-old rats this tubulin species accounts for 48% of the total soluble tubulin.
Abstract: The amount of total tubulin in the soluble fraction of rat brain was measured by a method based on the purification of tubulin previously labeled by incorporation of [14C]tyrosine in the C terminus of its α-chain. The tubulin content decreased from 2.01 to 1.30 nmol/mg protein when the animals passed from 4 to 30 days of age and then remained practically constant.
The amounts of aminoacylated and non-aminoacylated tubulin present in the soluble brain extracts were determined from the incorporation of [14C]tyrosine into the free acceptor sites of tubulin preparations, that were preincubated without carboxypeptidase A or with this enzyme to eliminate tyrosine and phenylalanine from the C terminus of the α-chain of tubulin. The values obtained were corrected for the inactivation of tubulin to accept [14C]tyrosine that occurred during the isolation and incubation of the soluble fractions. The ratio non-aminoacylated/aminoacylated tubulin increased from 1.62 ± 0.03 in the 4-day-old rats to 2.11 ± 0.17 in the 120-day-old rats. The aminoacylatable tubulin, that is the sum of aminoacylated plus non-aminoacylated tubulin, decreased from 1.71 to 0.75 nmol/mg protein from 4-day-old to 30-day-old rats respectively and then remained practically constant.
The amount of aminoacylatable tubulin is lower than that of total soluble tubulin. Therefore there is a fraction of tubulin that is unable to accept tyrosine. This non-aminoacylatable tubulin fraction increases with the age of the animal so that in the 120-day-old rats this tubulin species accounts for 48% of the total soluble tubulin.
TL;DR: A soluble enzyme which rapidly degrades both Met and Leu-enkephalin by cleavage of the Tyr-Gly bond has been identified in homogenates of corpora striata from human brain.
TL;DR: Modification and kinetic studies led to a conclusion that at least one tyrosine residue is involved in the active site of the enzyme, presumably participating in the initial reaction of the oxidation step of a propionate group to beta-hydroxypropionate.
Journal Article•
TL;DR: It is concluded that 7HDPT is a valuable agent for studying presynaptic mechanisms of tyrosine hydroxylase regulation in the rat striatum since its activity appears to be mediated primarily through presynptic plasma membrane dopamine receptors.
Abstract: Tyrosine hydroxylase activity in rat striatal synaptosomes was inhibited by four different dopamine agonists: dopamine (DA) (IC50 0.2 µM), apomorphine (APO) (IC50 = 0.1 µM), 6,7-dihydroxy-2-aminotetralin (ADTN) (IC50 0.2 µM), and 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7HDPT) (IC50 = 1.3 µM). The inhibitory activities of DA and ADTN were antagonized by the addition of the dopamine uptake inhibitor benztropine but not by the addition of the dopamine receptor antagonist fluphenazine. The inhibitory activity of APO was marginally antagonized by the addition of either benztropine or fluphenazine. The inhibitory activity of 7HDPT was antagonized by fluphenazine and other neuroleptics but not by benztropine. In contrast to the other agonists, 7HDPT did not inhibit soluble tyrosine hydroxylase assayed in the presence of the synthetic cofactor, 6,7-dimethyl-5,6,7,8-tetrahydropterine (DMPH4). The inhibition of synaptosomal tyrosine hydroxylase by 7HDPT was also antagonized by DMPH4, dibutyryl cAMP, and FeSO4 in the presence of β-mercaptoethanol but not by ATP, GTP, cAMP, or dibutyryl cGMP or by high concentrations (11 mM) of calcium. Incubation of synaptosomes with concentrations of 7HDPT which inhibited synaptosomal tyrosine hydroxylation by greater than 50% did not cause a significant change in the Vmax of tyrosine hydroxylase or the Km of tyrosine hydroxylase for the synthetic cofactor DMPH4. It is concluded that 7HDPT is a valuable agent for studying presynaptic mechanisms of tyrosine hydroxylase regulation in the rat striatum since its activity appears to be mediated primarily through presynaptic plasma membrane dopamine receptors. The mechanism by which presynaptic dopamine receptors may regulate tyrosine hydroxylase activity is discussed.
TL;DR: It appears that tyrosine supplementation was effective in reducing the effects of stress in the aged animals, possibly by virtue of its relationship to catecholamine metabolism.
Abstract: The effects of dietary supplements of L-tyrosine on aggressive behavior, locomotor activity, and brain neurochemical changes were assessed in young and aged mice following cold-swim stress. Male CF-1 mice, ages 3 months and 21 months, were maintained on a semi-synthetic basal diet for one week, pretested for aggressive behavior and locomotor activity, then switched to diets modified by the addition of tyrosine or casein (control). After one week on the diet supplements, half of the mice were stressed by cold water swim and all were again subjected to behavioral testing. Members of each group were sacrificed for analysis of amino acids and monoamines in brain tissue and corticosterones in blood. It was found that tyrosine supplementation induced a marked increase in aggressive behavior in young, nonstressed mice but not in aged mice. Stress decreased the aggressiveness of both young and aged mice, and tyrosine prevented this stress-induced decrease in both groups. Young mice exhibited no changes in locomotion as a function of stress or diet. However, tyrosine prevented decreases in locomotion observed on second testing of both stressed and nonstressed older mice. The effect of stress was to lower levels of brain norepinephrine (NE) and dopamine (DA) in both young and aged mice. Tyrosine supplementation increased brain tyrosine and DA in both groups. Brain serotonin levels were lower in the aged mice compared to the younger ones, and this was associated with relatively higher concentrations of 5-hydroxyindoleacetic acid. It appears that tyrosine supplementation was effective in reducing the effects of stress in the aged animals, possibly by virtue of its relationship to catecholamine metabolism.
TL;DR: It appears that neither serum-free phenylalanine nor serum- free tyrosine can be used to accurately predict dietary aromatic amino acid adequacy for the fingerling channel catfish.
Abstract: A series of experiments was conducted to determine the aromatic amino acid requirement, the tyrosine replacement value for phenylalanine and the phenylalanine requirement under conditions of adequate tyrosine for fingerling channel catfish. Effects of excessive dietary levels of tyrosine were also investigated. The studies were conducted utilizing casein and gelatinbased diets supplemented with crystalline L-amino acids to correspond to the pattern of 24% whole egg protein. Based on 8-week growth studies, the total dietary aromatic amino acid requirement for fingerling channel catfish was approximately 1.20 +/- 0.06% (50% of the dietary protein) of which about 50% could be supplied by tyrosine. The phenylalanine requirement per se, based on growth and feed efficiency, was determined to be 0.47 +/- 0.02% and 0.49 +/- 0.02%, respectively. High dietary levels of tyrosine (up to 10%) did not adversely affect performance of fingerling channel catfish. It appears that neither serum-free phenylalanine nor serum-free tyrosine can be used to accurately predict dietary aromatic amino acid adequacy for the fingerling channel catfish.
TL;DR: Relationship between growth velocity and muscle amino acid pattern was found, a poor growth rate was associated with an increase of nonessential and essential amino acids with the exception of valine.
TL;DR: It is demonstrated that this enzyme specifically phosphorylates tyrosine and that Gardner FeSV-transformed mink and rat cells exhibit constitutively higher levels of phosphotyrosine than nontransformed control cells.