Phosphoserine Phosphatase Research Articles

Effect of Adenosine 3',5'-Monophosphate on Serine Metabolism in Chick Tissues

The effect of cyclic 3',5'-AMP and supplemental dietary glycine upon de novo synthesis of serine metabolic enzymes in chick livers were examined. Chicks fed crystalline amino acid diets containing 2% glycine had approximately twofold the activity in liver for 3-phosphoglycerate dehydrogenase and phosphoserine phosphatase compared to liver tissue from chicks fed diets lacking in dietary glycine. Chicks subjected to daily intraperitoneal injections of cyclic 3',5'-AMP and fed diets containing no dietary glycine contained biosynthetic enzyme activity similar to glycine-fed chicks suggesting a correlation between glycine and cyclic AMP for serine enzyme induction. The elevated enzyme activity in liver of chicks fed dietary glycine or injected with cyclic AMP was inhibited when chicks were also injected with actinomycin D indicating de novo synthesis of 3-phosphoglycerate dehydrogenase and phosphoserine phosphatase. Dietary glycine or cyclic AMP, however, did not change serine dehydratase and glycerate dehydrogenase activities in chick liver.

Regulation of Enzymes of Serine and One-Carbon Metabolism by Testosterone in Rat Prostate, Liver, and Kidney1

A significant decrease in the specific activity of 3 enzymes of serine and one-carbon metabolism (3-phosphoglycerate dehydrgenase, phosphoserine phosphatase, and serine hydroxy-methyltransferase) was found in the rat prostate gland with castration. A single injection of testosterone propionate to rats 3 days after castration resulted in a significant increase in the 3 enzyme activities within 24 h. This increase in specific activity was maximal 72 h after injection of testosterone in the case of 3-phosphoglycerate dehydrogenase and serine hydroxymethyltransferase. When cycloheximide was administered in conjunction with testosterone, the increase in 3-phosphoglycerate dehydrogenase and serine hydroxy-methyltransferase activity was significantly reduced compared to injection of testosterone alone. N6, O2'-dibutyryl adenosine-3',5'-cyclic monophosphate [(Bu)2 cAMP] and theophylline injected at 8 h intervals to rats 3 days after castration failed to mimic the action of testosterone on these 3 enzymes 24 and 72 h after beginning injections. Castration had no effect on the specific activity of these enzymes in the kidney; however, 3-phosphoglycerate dehydrogenase was significantly diminished in the liver 6 days after castration. A single injection of testosterone to rats 3 days after castration restored the activity to sham-operated levels. Serine hydroxy-methyltransferase and phosphoserine phosphatase activity in the liver were unaffected 6 days after castration. Thus testosterone exerts a regulatory role on serine and one-carbon metabolism in the prostate and liver which (Bu), cAMP is unable to minic.

Effect of Various Concentrations of Protein in Chick Diet upon the Metabolic Enzymes of Glycine and Serine

The effect of feeding low protein diets with and without 2% glycine or 2% l-serine to chicks upon the enzymes concerned in the metabolism of glycine and serine has been determined. D-3-phosphoglycerate dehydrogenase (EC 1.1.1.s), phosphoserine phosphatase (EC 3.1.3.3), and serine hydroxymethyltransferase (EC 2.1.2.1) activities were significantly increased in livers from chicks fed 75% protein diets as compared to liver enzyme activities from chicks fed either 24% chick starter, 2% or 25% protein diets. Phosphoserine phosphatase activity was significantly higher in kidney tissue of chicks fed 75% protein diets. Livers from chicks fed 25% protein diets had a higher activity for D-3-phosphoglycerate dehydrogenase and phosphoserine phosphatase than did those fed chick starter or 2% protein diets. D-3-phosphoglycerate dehydrogenase and phosphoserine phosphatase activities were higher in livers from chicks fed 2% protein, 2% protein + 2% glycine, and 2% protein + 2% l-serine diets when compared to those from chicks fed low protein diets with supplemental methionine or cysteine. Serine dehydratase (EC 4.2.1.13), glycerate dehydrogenase (EC 1.1.1.29) and hydroxypyruvate-P: l-glutamate transaminase activities remained constant in livers from chicks fed all experimental diets. The uric acid concentration was significantly increased in plasma from chicks fed the high protein diets which suggests that D-3-phosphoglycerate dehydrogenase, phosphoserine phosphatase and serine hydroxymethyltransferase activities were increased because of the high requirement for glycine in uric acid formation. The 75% protein diet provided three times as much glycine as the 25% protein diet which may have met the increased need for glycine for uric acid formation.

Distribution Studies of Glycine and Serine Enzymes in Chicks

Day-old broiler type chicks were fed a practical starter ration for three weeks, sacrificed and the D-3-phosphoglycerate dehydrogenase (E.C. 1.1.1.s), phosphoserine phosphatase (E.C. 3.1.3.3), glycerate dehydrogenase (E.C. 1.1.1.29), hydroxypyruvate-P:glutamate transaminase, serine transhydroxymethylase (E.C. 2.1.2.1), and serine dehydratase (E.C. 4.2.1.13) enzyme activities were determined in liver, kidney, heart, spleen and brain tissue in evaluating glycine and serine metabolism. The distribution of the various glycine and serine biosynthetic enzymes in the chick tissues studied show that the major portion of glycine and serine synthesis occurs in hepatic tissue via the “phosphorylated pathway.”

Formula omitted] phosphatase from bovine brain and kidney : High molecular weight forms occurring during the purification

O- Phosphoserine phosphohydrolase (EC 3.1.3.3) from bovine brain and kidney was found to exist in several molecular forms, which can be separated by chromatography on Sephadex gels. This is the consequence of a self-association process, that appears at any purification step when extracts containing the brain or kidney enzymes are precipitated with (NH 4) 2SO 4 at pH 7.5 but does not appear when other concentrating methods of concentration are used or if the (NH 4) 2SO 4 precipitations are made at pH 5.0 or lower. β-Mercaptoethanol prevents the formation of associated forms and dissociates them when they are present. N- Ethylmaleimide also prevents their formation. It is suggested that disulfide bonds are involved in this self-association process. From these observations, phosphoserine phosphatase from bovine kidney has been partially purified 170-fold in the unassociated form and 270-fold in the associated forms. Some properties of these two species of enzyme are also compared in this paper.

Enzymes of serine biosynthesis in Rhodopseudomonas capsulata

Rhodopseudomonas capsulata has been shown to possess all the enzymatic activities of both the phosphorylated and nonphosphorylated pathways of serine biosynthesis. In addition there was an active serine hydroxymethyltransferase which catalyzed the reversible interconversion of serine and glycine. In cells grown photosynthetically with malate as the carbon source, the activities of the phosphorylated pathway enzymes were substantially higher than the analogous reactions of the nonphosphorylated sequence. l-Serine (1 m m) caused approximately 60%, inhibition of the first enzyme of the phosphorylated route, 3-phosphoglyceric acid dehydrogenase, but was less effective in inhibiting the last enzyme, phosphoserine phosphatase. Glycine also exerted a regulatory effect on this pathway but it was not as potent an inhibitor as serine. The inhibitions caused by serine and glycine were simply additive; there was no evidence of concerted feedback inhibition of the phosphorylated pathway by these amino acids.

Genetic and physiological control of serine and glycine biosynthesis in Saccharomyces.

Two of the three known metabolic pathways to serine and glycine have been shown to be present in prototrophic yeast strains, i.e., the phosphorylated pathway from glycolytic intermediates and the glyoxylate pathway from tricarboxylic acid cycle intermediates. Two serine-glycine auxotrophs (ser1 and ser2) were found to be blocked in the phosphoglycerate pathway. The ser1 gene controls l-glutamate:phosphohydroxypyruvate transaminase biosynthesis, and the ser2 gene controls phosphoserine phosphatase biosynthesis. The other pathway to glycine, from isocitrate, is repressed by growth in glucose media, specifically, at isocitrate lyase and at the alanine:glyoxylate transaminase. This pathway is derepressed by growth to stationary phase in glucose media yielding high activity of these enzymes. The phosphorylated pathway appears to be the principal biosynthetic pathway to serine and glycine during growth on sugar media. Strains which are serine-glycine dependent in glucose media became capable of serine-glycine independent growth on acetate media. These results describe a method of physiological control of a secondary metabolic pathway allowing a single lesion in the principal biosynthetic pathway to produce auxotrophy. This may be termed conditional auxotrophy.

The biosynthesis of serine and glycine in Pseudomonas AM1 with special reference to growth on carbon sources other than C1 compounds.

1. A mutant, 20S, of Pseudomonas AM1 was obtained that requires a supplement of serine to grow on succinate, lactate or ethanol. This mutant lacks phosphoserine phosphatase and revertants to wild-type phenotype regained this enzymic activity showing that the phosphorylated pathway of serine biosynthesis is necessary for growth on these three substrates. 2. The requirement for supplemental serine by mutant 20S could be met by glycine, suggesting that Pseudomonas AM1 can obtain C(1) units from glycine. 3. Mutant 20S grows on C(1) compounds at a lower rate compared with the wild type. Supplementation with serine stimulated the growth rate of the mutant suggesting that the phosphorylated pathway of serine biosynthesis plays some role, but not an essential role, during growth on C(1) compounds. 4. A mutant, 82G, was obtained that requires a supplement of glycine to grow on succinate, lactate or ethanol. When grown in such supplemented media, the mutant lacks serine hydroxymethyltransferase and revertants to wild-type phenotype regained enzymic activity showing that during growth on succinate, lactate or ethanol, glycine is made from serine via serine hydroxymethyltransferase, and that the organism can obtain C(1) units from glycine. 5. Mutant 82G grew on methanol and then contained serine hydroxymethyltransferase suggesting that this enzyme is necessary for growth on C(1) compounds and that Pseudomonas AM1 may synthesize two such enzymes, one used in growth on C(1) compounds, the other used in growth on other substrates. Mutant 82G might lack the latter enzyme. 6. Phosphoglycerate dehydrogenase is specifically inhibited by l-serine and the regulatory implications of this are discussed.

Phosphoserine phosphatase: Development formation and hormonal regulation in rat tissues

Phosphoserine phosphatase was measured in rat liver and kidney as a function of age, sex, and treatment with different endocrine or metabolic factors. Several differences were found between liver and kidney in the regulation of this enzyme. The phosphoserine phosphatase activity of adult liver was 595 units per g for males, 383 for females, and for adult kidney of both sexes it was 1266. Estrogen treatment raised the level of phosphoserine phosphatase in kidneys after the age of 25 days but not in livers. The high levels of phosphoserine phosphatase in fetal liver, 2500 units per g, decreased to 900 during the last 4 days of gestation and the first 3 postnatal days. During the same time period kidney phosphoserine phosphatase increased from insignificant levels to about 600 units per g. The administration of hydrocortisone (but not of thyroxine, glucagon, or serine) to fetal rats enhanced the decline of liver phosphoserine phosphatase, suggesting that adrenocortical secretion is the stimulus for the normal decrease in liver phosphoserine phosphatase during late fetal life. The injection of hydrocortisone to the pregnant rat also resulted in lower phosphoserine phosphatase in the livers of her fetuses or newborns.

Purification of mouse brain phosphoserine phosphohydrolase and phosphotransferase

Mouse brain phosphoserine phosphatase (EC 3.1.3.3.) that has been partially purified 150-fold or greater tolerates heating at 52 ° for several hours, resulting in a preparation that is 1200- to 1500-fold enriched over an aqueous homogenate of brain. Sucrose-gradient centrifugation of the purified enzyme shows one symmetrical peak of activity, with an estimated molecular weight of about 47,000. The enzyme, which underwent prolonged heating during purification, retains its sensitivity to inhibition by l-serine. However, the degree of inhibition is dependent upon the incubation temperature, with elevated temperature decreasing the effectiveness of serine as an inhibitor. The inhibition by serine of the phosphohydrolysis of phosphoserine is compatible with an ordered release of products, with serine released first. The enzyme also catalyzes a phosphoryl group transfer from phosphoserine to serine. Preliminary analysis of this activity is also consistent with a mechanism whereby there is an ordered product release.

Phosphoserine phosphatase distribution in normal and neoplastic rat tissues

Optimal conditions for assay of phosphoserine phosphatase by phosphate release were determined in dialyzed rat tissue extracts. Hydrolysis that was specifically inhibited by 10 m m l-serine was used to measure the enzyme activity. Nonspecific reactions were minimal. Phospho- d-serine was the preferred substrate since it avoided inhibition by the product of the reaction. Significant activities were present in normal adult kidney, liver, spleen, and brain, and extremely low activities in heart and breast. Relatively high activities in fetal liver, lactating mammary gland, and tumors suggested a parallel between enzyme level and tissue growth or protein synthesis. Marked activity changes occurred physiologically with development of liver and kidney.

The effects of dietary protein on the hepatic enzymes of serine metabolism in the rabbit

The hepatic levels of activity of seven enzymes involved in serine metabolism have been measured in rabbits fed diets of varying protein content. Rabbits fed an 88% casein diet for 14 days had a marked increase in the activities of hydroxypyruvate: l-alanine transaminase, d-glycerate kinase, and serine dehydratase, and a significant decrease in the activities of 3-P-glycerate dehydrogenase, P-hydroxypyruvate: l-glutamate transaminase, and phosphoserine phosphatase, when compared to rabbits fed chow. Conversely, when a 2% casein diet was fed to the animals for the same time period, the hepatic activities of hydroxypyruvate: l-alanine transaminase, d-glycerate kinase, and serine dehydratase were lowered and that of 3-P-glycerate dehydrogenase was elevated over values found in chow-fed rabbits. No significant changes in the level of activity of d-glycerate dehydrogenase were observed with any of the diets investigated. Preliminary experiments with puromycin suggest that the observed increase in the hepatic level of activity of hydroxypyruvate: l-alanine transaminase in rabbits maintained on an 88% casein diet may be due to an altered rate of enzyme synthesis. The results are discussed with reference to serine anabolism and catabolism in rabbit liver.

Mouse Brain Phosphoserine Phosphohydrolase and Phosphotransferase

Abstract Phosphoserine phosphatase has been partially purified from mouse brain. The preparation catalyzes the phosphohydrolysis of phosphoserine at an optimal pH of about 6.2. This hydrolysis is strongly inhibited by serine. The preparation also catalyzes an exchange reaction whereby the phosphoryl group of phosphoserine is transferred to serine at an optimal pH of about 7.5. Treatment with urea results in inhibition of the hydrolytic activity and enhancement of the transferase activity. Conversely, transferase activity is inhibited by sucrose while the hydrolase activity or its inhibition by serine is unaffected. These iindings are not compatible with a mechanism that equates serine's activity as an inhibitor of hydrolysis with serine's role as a substrate in phosphotransferase. It is suggested that these two activities may be separate phenomena.

Synthesis of serine in the liver of vertebrates

1. 1. The radioactivity of uniformly labeled C 14-glucose is incorporated into phosphoserin and serine by liver extracts of rat, guinea pig, chicken, pigeon and turtle and into serine by liver extracts of frog, tench and eel. 2. 2. The technique of isotope competition shows that serine sythesis occurs through the phosphorylated pathway as well as through the non-phosphorylated one in rat, guinea pig and chicken, whereas in pigeon liver only the first one is operative. 3. 3. 3-Phosphoglycerate dehydrogenase and phosphohydroxypyruvate-glutamate transaminase are present in the liver of all the animals which we have studied, in contrast to phosphoserine phosphatase, which is absent in some of them (frog, tench and eel). 4. 4. Hydroxypyruvate-alanine transaminase is active in the liver of rat, guinea pig, chicken, frog, tench and eel, but not in pigeon and turtle liver. 5. 5. Serine-hydroxymethyltransferase is active in all the vertebrates which we have studied.

Serine Biosynthesis in Rat Liver: REGULATION OF ENZYME CONCENTRATION BY DIETARY FACTORS

Abstract 3-Phosphoglycerate dehydrogenase, phosphoserine phosphatase, d-glycerate dehydrogenase, and serine dehydratase have been measured in rats fet diets containing variable amounts of protein. Rats fed 2% casein diets for 7 days had a marked increase in 3-P-glycerate dehydrogenase and P-serine phosphatase and a simultaneous decline in serine dehydratase when compared to rats fed chow or a 25% casein diet. The increased enzyme levels were prevented by the addition of 1% cysteine to the 2% casein diet but this did not alter the decline in serine dehydratase. On 88% casein diets a depression of 3-P-glycerate dehydrogenase and P-serine phosphatase resulted, while prompt increase in serine dehydratase occurred. No reproducible changes in d-glycerate dehydrogenase occurred on any of the diets studied. The administration of actinomycin D on several schedules consistently caused an inhibition of the changes noted with the 2% casein diet. These observations plus studies with cycloheximide suggest that the observed alterations in enzyme concentrations may be mediated by altered rates of enzyme synthesis. Studies of potential feedback inhibitors of the reactions measured were negative for 3-P-glycerate dehydrogenase and d-glycerate dehydrogenase. Inhibition of P-serine phosphatase by l-serine may have physiological significance in mammals. The inhibition of serine dehydratase by l-cysteine is described.

Phosphoserine phosphatase of vertebrates

1. 1. Phosphatase activity of phosphoserine has been measured in the liver of rat, guinea-pig, rabbit, chicken, duck, pigeon, goose, turtle, frog, tench and eel. 2. 2. The liver of all the animals which we have studied is capable of splitting phosphoserine, but only rat, chicken and turtle liver contains a specific phosphoserine phosphatase. This is absent in the liver of frog, tench and eel. 3. 3. Phosphoserine phosphatase of turtle liver is strongly inhibited by l-serine and, to a lesser degree, by l-serine. It requires Mg 2+ for the activity. Co 2+ and Ni 2+ can substitute for Mg 2+. 4. 4. Liver of guinea-pig and pigeon contains a very active acid phosphatase, whilst an alkaline phosphatase is present in turtle, frog and tench liver.