Formation Of Serine Research Articles

LIPID METABOLISM IN LEAVES OF TUSSILAGO FARFARA DURING INFECTION BY PUCCINIA POARUM

SUMMARYFollowing infection by Puccinia poarum, there is an accumulation of lipid in leaf tissue of Tussilago farfara. Most of this increase is in the fungus, which accounts for nearly half of the dry weight of mature aecial pustules. While the lipid content of infected tissue rises to more than three times that of healthy leaves, that of the uninfected parts of diseased leaves is reduced by one‐third. Aerial pustules accumulate a high proportion of neutral lipid, particularly triglycerides and fatty acids. As infection progresses, a loss of chloroplast glycolipids and phosphatidyl glycerol is accompanied by increases in phosphatidyl ethanolamine and phosphatidyl choline and the formation of phosphatidyl serine, which is not readily detectable in healthy leaf tissue. The lipid changes following rust infection have been compared with those of senescing Tussilago leaves.Both neutral lipids and phospholipids incorporated more photosynthetically assimilated C in rust‐infected tissue than in healthy leaves. Greatest differences were in free fatty acids, triglycerides, phosphatidyl ethanolamine and phosphatidyl choline with significant increases also in sterols, phosphatidyl inositol and phosphatidyl serine. Whereas three‐quarters of the activity incorporated from 14CO2 into lipid appears in the neutral lipids of diseased tissue, in healthy tissue these contain only one‐quarter.

Effect of CO2 Concentration on Glycine and Serine Formation during Photorespiration

Amount and products of photosynthesis during 10 minutes were measured at different (14)CO(2) concentrations in air. With tobacco (Nicotiana tabacum L. cv. Maryland Mammoth) leaves the percentage of (14)C in glycine plus serine was highest (42%) at 0.005% CO(2), and decreased with increasing CO(2) concentration to 7% of the total at 1% CO(2) in air. However, above 0.03% CO(2) the total amount of (14)C incorporated into the glycine and serine pool was about constant. At 0.005% or 0.03% CO(2) the percentage and amount of (14)C in sucrose was small but increased greatly at higher CO(2) levels as sucrose accumulated as an end product. Relatively similar data were obtained with sugar beet (Beta vulgaris L. cv. US H20) leaves. The results suggest that photorespiration at high CO(2) concentration is not inhibited but that CO(2) loss from it becomes less significant.

Studies on the enzymes involved in the biosynthesis of cyclo-tris (N-2,3-dihydroxybenzoyl-L-seryl) in Escherichia coli: kinetic properties of the L-serine-activating enzyme.

Some kinetic properties of the formation of a thioester-bound l-seryl-enzyme intermediate are described. The rate constant of formation is 3.12 x 10(2) M(-1) s(-1) and the rate constant for spontaneous breakdown is 2.47 x 10(-3) s(-1). These constants yield a value of log K = 5.10 for the overall equilibrium constant which agrees favorably with a value of 5.20 calculated from equilibrium binding data. E(1).serine formation requires a thiol group which is extremely reactive to N-ethylmaleimide; the second-order rate constant for enzyme inactivation by this reagent is 77.1 M(-1) s(-1) at pH 6.6 and 0 C. Excess l-serine does not protect the enzyme against inactivation. In addition to an adenosine triphosphate-[(32)P]-inorganic pyrophosphate exchange, the enzyme also catalyzes an l-serine-dependent adenosine triphosphate-[(3)H]adenosine monophosphate exchange in accordance with the scheme proposed for the activation of serine.

Experimental studies on sulfur dioxide injuries in higher plants

Photosynthesis is reversibly inhibited by exposing plants to SO2. The formation of α-hydroxy sulfonate in the exposed plants is suggested as one of the effects, because this compound inhibits glycolic oxidase which is necessary in the glycolic acid pathway. The suppression of the glycolic acid path should affect various aspects of metabolism in plants, particularly the reduction of the biosynthesis of glycine and serine. In this paper, the biosynthesis of these amino acids in plants exposed to SO2 was investigated to estimate the significance of the formation of α-hydroxy sulfonate in the plants. The results show that photosynthetic formation of serine was reduced in the exposed plants, and that α-hydroxy sulfonate was formed.

Serine biosynthesis in Tetrahymena pyriformis S

1. 1. Glycine transhydroxymethylase and threonine aldolase function in the formation of serine in Tetrahymena pyriformis S. 2. 2. Both the phosphorylated and non-phosphorylated pathways of serine biosynthesis from 3-phosphoglycerate are also operative. 3. 3. Tricarboxylic acid cycle intermediates also serve as serine precursors in this organism. 4. 4. Pyruvate, short chain fatty acids, and at low concentrations, α-ketoglutarate, appear to serve as energy sources for serine incorporation.

Isovaleric Acidemia Presenting with Altered Metabolism of Glycine

Extract: A 7-year-old girl with periodic acidosis, lethargy, and coma beginning during the 1st year of life was studied. Episodes of ketoacidosis usually occurred with minor respiratory or gastrointestinal infections. There was history neither of peculiar body odor nor characteristic smell like that of sweaty feet. Hyperglycinemia, 4.2 mg/100 ml, and hyperglycinuria, 361 mg/liter, were found at times of illness with acidosis. A clinical diagnosis of ketotic hyperglycinemia was made in 1966. Glycine metabolism was therefore investigated in vivo using 14C-labeled glycine. The oxidation of glycine to respiratory CO2 and formation of serine from glycine were found to be normal. The labeling of urinary hippurate, however, the largest component of the labeled products of glycine in the urine in normal individuals, was virtually zero. An abnormal, labeled product of glycine was found in the urine and identified as isovalerylglycine. As much as 6% of the 14C-glycine administered was incorporated into urinary isovalerylglycine within 24 hr. Isovalerylglycine in urine was 2880 mg/24 hr, while normal individuals excrete less than 2 mg/24 hr. Isovaleric acid was found in both urine and plasma. Isovaleric acid in the plasma and urine, 2.86 mg/liter and 2.56 mg/day, respectively, was only five to six times larger than that found in normal individuals. Formation and excretion of isovalerylglycine may be a compensatory mechanism for the elimination of toxic amounts of isovaleric acid from the body. Biosynthesis of such huge amounts of isovalerylglycine may alter the overall metabolism of glycine. Isovaleric acidemia may present with hyperglycinemia and hyperglycinuria. Examination of the urine for isovalerylglycine is a convenient method for detecting the syndrome of isovaleric acidemia. Speculation: Isovaleric acidemia, in common with propionic acidemia with ketotic hyperglycinemia and methylmalonic acidemia, produces dramatic episodes of ketoacidosis. It is now clear that, like these conditions, isovaleric acidemia can also produce leukopenia and elevated concentrations of glycine in body fluids. The mechanisms causing these abnormalities are unknown. Elucidation of metabolic interfaces among these conditions could lead to understanding of the pathophysiology involved.

Studies on Adrenal Steroid Hydroxylases: THE REACTIVITY OF TRIPHENYL PHOSPHINE WITH LABILE SULFUR IN ADRENAL IRON-SULFUR PROTEIN (ADRENODOXIN)

Abstract The labile sulfur of adrenodoxin was attacked by a nucleophile, triphenyl phosphine. The product was triphenyl phosphine sulfide regardless of the presence of O2. The stoichiometry between labile sulfur which disappeared and triphenyl phosphine sulfide formed was found to be 1:1. The initial rate of the reaction follows second order kinetics with a rate constant of 2 to 3 x 103 m-1 min-1 at 38° (pH 8.8) under aerobic and anaerobic conditions. The product of the minor reaction was found to be pyruvate after acid hydrolysis of the protein. The amount of pyruvate formed (about 1 mole per mole of protein) is roughly equal to those of cysteine residues lost and H2S evolved. There was no significant formation of alanine and serine by this reaction. The triphenyl phosphine-treated protein has no iron, no labile sulfur, one disulfide bond, 1 dehydroalanine, and 2 cysteine residues per molecule of the protein. On the basis of these observations, it is concluded that, upon reaction of triphenyl phosphine with adrenodoxin, the labile sulfur is removed as the phosphine sulfide, and that one of the sulfur atoms of the cysteine residues is liberated as H2S and results in the dehydroalanine residue in the polypeptide chain, which is quantitatively converted into pyruvate upon acid hydrolysis. This phenomenon is in contrast with the acid treatment which removes the labile sulfur as H2S but does not produce dehydroalanine. From the results of the triphenyl phosphine reactivity of model metal-sulfur compounds, Ni(C6H5CS3)(C6H5CS2) and Fe(C6H5CS3)2(C6H5CS2),it would be likely that the iron-sulfur grouping of adrenodoxin as its oxidation-reduction center consists of Fe—S—S— linkage, because the above model compounds contain the metal—S—S— linkage, as judged by x-ray crystallography (D. Coucouvanis and S. J. Lippard, J. Amer. Chem. Soc., 90, 3281 (1968)), and they react with triphenyl phosphine to yield its sulfide.

Regulatory effects of ammonia on carbon metabolism in photosynthesizing Chlorella pyrenoidosa

Addition of ammonia to Chlorella pyrenoidosa, photosynthesizing under steady-state conditions, causes changes in the metabolism which are due not only to the increased availability of NH 4 + for reductive amination but also to regulation of controlled enzymes. One such effect is an increased rate of the reaction which converts phosphoenolpyruvate to pyruvate in vivo. This regulatory effect was revealed by kinetic tracer studies with 14CO 2, paper chromatography and radioautographic analysis, which showed that upon addition of NH 4 + (1) the levels of both 3-phosphoglycerate and phosphoenolpyruvate drop, with the ratio of 3-phosphoglycerate/phosphoenolpyruvate increasing, (2) the level of labeled pyruvic acid increases and the rate of formation of alanine increases rapidly, while the rate of formation of serine is unaffected, (3) the rate of flow of carbon into the tricarboxylic acid cycle acids, malate and citrate, increases along with the increased rates of formation of glutamate, glutamine and aspartate and (4) the rate of labeling of lipids increases. The increased flow of carbon into amino acids is mostly at the expense of sucrose synthesis; starch synthesis decreases only slightly. The interruption of sucrose synthesis apparently is due to stopping the reaction between UDP-glucose and fructose 6-phosphate. The rate of conversion of fructose 1,6-diphosphate to fructose 6-phosphate is also decreased upon NH 4 + addition.

Lipid metabolism in human platelets

Washed human platelets were incubated with radioactive glycerol; the platelets were able to synthesize de novo the major phosphoglycerides including phosphatidic acid, phosphatidylinositol, phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine. The specific activities of the phosphoglycerides obtained after glycerol incorporation indicate that phosphatidic acid, phosphatidylinositol, and phosphatidyl choline are metabolically active relative to phosphatidyl ethanolamine and that formation of phosphatidyl serine occurs to a much more limited extent. When platelets were incubated with bovine thrombin, 1 U/ml, the pattern of glycerol incorporation into phospholipid was changed. There was a 3-fold decrease in the total incorporation into lipid in 30 min with a relative 5-fold decreased incorporation into phosphatidyl choline and phosphatidyl ethanolamine and a 5-fold increased incorporation into phosphatidyl serine. The increased incorporation into phosphatidyl serine. The increased incorporation into phosphatidyl serine was maximal within the first 2 min but was transient, since within 20 minutes, the rate returned to that seen in platelets incubated with glycerol alone. Purified human thrombin also produced this same effect on phospholipid synthesis in platelets. Trypsin produced effects on phosphoglyceride formation similar to those seen with thrombin, and the trypsin-induced effect was inhibited by prior incubation of trypsin with soybean trypsin inhibitor, suggesting that proteolysis may be required for the observed effects on phospholipid synthesis.

The glycollate pathway during the photoassimilation of acetate by Chlorella

When Chlorella pyrenoidosa photoassimilates 3H−14C-acetate glycollic acid rapidly becomes labelled with both tritium and 14C. The 3H/14C ratio was 10 in glycollate, (compared with 4 in the acetate added) and the only other intermediates showing similar 3H/14C ratios to glycollate were glycerate and serine. This suggests a glycollate pathway for the formation of serine was operating in Chlorella pyrenoidosa during the photoassimilation of acetate. When Chlorella pyrenoidosa assimilated 3H−14C-acetate in the dark glycollate was not labelled with either 14C or tritium. Although glycerate and serine both became labelled with 14C and tritium in the dark they did not show the high 3H/14C ratios recorded in the light. When cells were aerated with unlabelled 5% CO2 during the photoassimilation of 3H−14C-acetate, the 3H/14C ratios of glycollate, glycerate and serine were slightly decreased. Similarly, under anaerobic conditions in the light the 3H/14C ratio was decreased compared with aerobic conditions.

Glycolate pathway in algae.

No glycolate oxidase activity could be detected by manometric, isotopic, or spectrophotometric techniques in cell extracts from 5 strains of algae grown in the light with CO(2). However, NADH:glyoxylate reductase, phosphoglycolate phosphatase and isocitrate dehydrogenase were detected in the cell extracts. The serine formed by Chlorella or Chlamydomonas after 12 seconds of photosynthetic (14)CO(2) fixation contained 70 to 80% of its (14)C in the carboxyl carbon. This distribution of label in serine was similar to that in phosphoglycerate from the same experiment. Thus, in algae serine is probably formed directly from phosphoglycerate. These results differ from those of higher plants which form uniformly labeled serine from glycolate in short time periods when phosphoglycerate is still carboxyl labeled. In glycolate formed by algae in 5 and 10 seconds of (14)CO(2) fixation, C(2) was at least twice as radioactive as C(1). A similar skewed labeling in C(2) and C(3) of 3-phosphoglycerate and serine suggests a common precursor for glycolate and 3-phosphoglycerate. Glycine formed by the algae, however, from the same experiments was uniformly labeled. Manganese deficient Chlorella incorporated only 2% of the total (14)CO(2) fixed in 10 minutes into glycolate, while in normal Chlorella 30% of the total (14)C was found in glycolate. Manganese deficient Chlorella also accumulated more (14)C in glycine and serine.Glycolate excretion by Chlorella was maximal in 10 mm bicarbonate and occurred only in the light, and was not influenced by the addition of glycolate. No time dependent uptake of significant amounts of either glycolate or phosphoglycolate was observed. When small amounts of glycolate-2-(14)C were fed to Chlorella or Scenedesmus, only 2 to 3% was metabolized after 30 to 60 minutes. The algae were not capable of significant glycolate metabolism as is the higher plant. The failure to detect glycolate oxidase, the low level glycolate-(14)C metabolism, and the formation of serine from phosphoglycerate rather than from glycolate are consistent with the concept of an incomplete glycolate pathway in algae.

Glycolate, Glycine, Serine, and Glycerate Formation during Photosynthesis by Tobacco Leaves

Formation of 3-phosphoglycerate, glycolate, glycerate, and serine by tobacco leaves was analyzed between 4 and 60 sec of 14CO2 fixation during photosynthesis. With decreasing time, the percentage of the total 14C incorporated into 3-phosphoglycerate increased; the percentage into the other compounds, including glycolate, decreased to nearly zero. At 4 or 11 sec 3-phosphoglycerate and glycerate were predominantly carboxyl labeled; glycolate was uniformly labeled. At 4 sec the specific activity of the carboxyl group of 3-phosphoglycerate was about 100-fold greater than that of either carbon atom of glycolate. Carbon atoms 2 and 3 of 3-phosphoglycerate were uniformly labeled at 4 or 11 sec and had a 10-fold higher specific activity than the carbon atoms of glycolate. 3-Phosphoglycerate became uniformly labeled between 30 and 60 sec, and the specific activities of carbon atoms of 3-phosphoglycerate and glycolate became similar. Addition of α-hydroxy-2-pyridinemethanesulfonate did not alter the initial rates of labeling or specific activity of 3-phosphoglycerate or glycolate, but glycolate-14C accumulated while the percentage of 14C decreased in products formed from glycolate, such as glycine, serine, glycerate, and sucrose. Glycine, like glycolate, was uniformly labeled even at the shortest times. After 4 sec serine was equally labeled in carbon atoms 1 and 2. Carbon atom 3 was slightly less active. In 11 sec serine was uniformly labeled. Results were consistent with serine formation from glycolate and glycine and a small unlabeled C1 pool. After 4 sec in the presence of the glycolate oxidase inhibitor, the small amount of labeled serine was slightly carboxyl labeled, as if part of the serine came from 3-phosphoglycerate. In 60 sec, tobacco leaves incorporated 12% of the total 14C in glycerate. The percentage distribution of 14C in glycerate carbon atoms was similar to that in 3-phosphoglycerate. The specific activity of glycerate carbon atoms was one-one hundredth that of 3-phosphoglycerate at 4 and 11 sec and one-tenth that of 3-phosphoglycerate at 60 sec.

Comparative Studies on the Pathways for Serine Biosynthesis in Animal Tissues

Abstract The pathways of serine biosynthesis utilizing either phosphorylated or nonphosphorylated intermediates have been investigated in a variety of tissues from different species of animals. The levels of activity of hydroxypyruvate phosphate:l-glutamate and hydroxypyruvate:l-alanine transaminases were determined, and their distribution was compared with that previously reported for d-glycerate 3-O-phosphate and d-glycerate dehydrogenases. Direct comparisons were made between the extent of the over-all conversion of d-glycerate to serine and of d-glycerate 3-O-phosphate to serine 3-O-phosphate catalyzed by liver preparations from six species. Additional studies were carried out on the specificity of the amino donor participating in transamination reactions with hydroxypyruvate in different tissues. The results indicate that although both pathways are functional in animal systems, the relative contribution by each pathway for the synthesis of serine is not the same for all tissues. For example, in dog and frog liver, the major pathway for the formation of this amino acid involves nonphosphorylated intermediates. In these two tissues, as well as in rabbit liver, it has been clearly shown that the amino donor for hydroxypyruvate transamination is alanine. Glutamine has been demonstrated to be the most effective amino donor for this reaction in rat kidney and liver. In contrast to these results, serine formation in beef and chicken liver has been shown to take place primarily by the phosphorylated pathway. In other tissues, e.g. pig liver and dog kidney, considerable serine biosynthesis occurs by both the phosphorylated and nonphosphorylated routes.

Pathways for the metabolism of glyoxylate and acetate in germinating fatty seeds.

Cotyledons of germinating sunflower, pumpkin, linseed, and watermelon seeds and the endosperm of germinating castor bean seeds have been examined for their ability to utilize glyoxylate-C14and acetate-C14for the biosynthesis of amino acids. All of the tissues examined readily utilized these acids when supplied in micromolar amounts to tissue slices. The chief products of this utilization included the organic acids of the glyoxylate and tricarboxylic acid cycles and a number of amino acids and amides. The results are interpreted as indicating that, in sunflower, watermelon, linseed, and pumpkin seeds, malate formed in the malate synthetase reaction is metabolized by the partial reactions of the tricarboxylic acid cycle. α-Ketoglutarate produced by these reactions is extensively utilized in the biosynthesis of glutamate, γ-aminobutyrate, and glutamine. In agreement with data already published, castor bean endosperm utilized acetate for the biosynthesis of sugars. This tissue also utilized glyoxylate for the formation of glycine, serine, glycollate, and malate. It is concluded that, with the exception of castor bean endosperm, acetyl CoA arising as a result of fatty acid oxidation might be utilized for amino acid biosynthesis via the partial reactions of the glyoxylate and tricarboxylic acid cycles.

HYPERGLYCINEMIA. V. THE MISCIBLE POOL AND TURNOVER RATE OF GLYCINE AND THE FORMATION OF SERINE.

HYPERGLYCINEMIA. V. THE MISCIBLE POOL AND TURNOVER RATE OF GLYCINE AND THE FORMATION OF SERINE.

Formation of Serine and Threonine Dehydratases During the Growth Cycle of Escherichia coli. Evidence of Two Different Enzymes.

Formation of Serine and Threonine Dehydratases During the Growth Cycle of Escherichia coli. Evidence of Two Different Enzymes.

Fructose as a precursor of amino acids in the lactating cow

The biosynthesis of amino acids from fructose and glucose uniformly labeled with C14 was studied in lactating cows. There were no major differences in the hexoses as precursors of amino acids, the injection of either hexose resulting in the formation of serine and alanine with highest specific activities. Amino acids from whey protein had the same C14 distribution as casein amino acids. Cystine was synthesized by the cow, but only to a small extent from fructose.

Studies on hydroxyamino acids. I. Synthesis of some α-alkylated serines

The coproduct which accompanies serine formation upon treatment of an aqueous alkaline solution of glycine with formaldehyde, in the presence of catalytic amounts of cupric ion, has been identified as α-(hydroxymethyl)serine. The latter product, which could be induced to form almost exclusively in the same reaction system solely by increasing the cupric ion concentration, was characterized by ( a) decarboxylation with ninhydrin, ( b) deamination with nitrous acid, ( c) oxidative degradation with periodate and ( d) reduction with hydriodic acid. An alternate synthesis of this material was achieved in high yield via the cupric ion-mediated condensation of serine and formaldehyde in alkaline aqueous solution. Substitution of the serine component in the last-mentioned reaction with alanine permitted the facile single-step synthesis of α-methylserine; comparable substitution with α-amino-n-butyric acid led to α-ethylserine.

Amino acid synthesis from formaldehyde and hydroxylamine

The experiments reported here have shown that by heating an aqueous mixture of formaldehyde and hydroxylamine hydrochloride, several amino acids, hydroxy acids, and other biochemical compounds are formed. The predominant amino acid formed is glycine. The conditions under which the reaction takes place have been studied in some detail. The mechanism of synthesis has also been studied. Formaldoxime, hydrogen cyanide, and ammonia are among the first products formed. Strecker and cyanohydrin condensations yield nitriles which are subsequently hydrolyzed to amides and finally to acids. Other condensation reactions are proposed to account for the formation of serine, alanine, β-alanine, and lactic acid. The interpretation of some previous photochemical syntheses of amino acids appears possible in the light of the present evidence. The experiments are of significance in relation to the formation of biochemical compounds, from simple compounds of carbon and nitrogen, under conditions assumed to have existed during the early development of the earth's crust.

The formation of glycine and serine: Calculation of certain reaction rates in the rat

The mathematical theory necessary for the calculation of the rates of synthesis and interconversion of serine and glycine in the rat has been developed. Values for these rates calculated from published data are: net conversion of serine into glycine in the absence of dietary glycine and serine, 1; synthesis of glycine from precursors other than serine, 1; synthesis of serine from precursors other than glycine, 2; gross conversion of serine into glycine, 6; gross conversion of glycine into serine, 5 mmole/100 g. body weight/day. The use of isotopic dilution as a measure of a rate of biosynthesis has been discussed.