3-carbon Compounds Research Articles

Alanine racemase of Pseudomonas: Observations on subtrate and inhibitor specificity

Systematic studies with purified alanine racemase and a number of substrate analogs permit the generalization that effective competitive inhibition is limited to 2- and 3-carbon compounds. A free α-amino group was not necessary for relatively tight binding; compounds lacking an amino group, or with an α-amino group acylated even by a bulky substituent, were bound as tightly as alanine. Substitution at the α-carbon of alanine (i.e., replacement of the α-H) eliminated binding, while substitution at the β-carbon generally reduced binding. Of several inhibitory compounds tested for substrate activity by H exchange with 3H 2O, only glycine appeared active. Covalent binding to the enzyme by halo analogs was not demonstrated.

Distribution of 14C-isotope in stereoisomers of serine.

A method is described for the analysis of the intramolecular distribution of 14C-isotope in micromole amounts of low activity L-serine. The 3-carbon compound is degraded enzymically with L-serine dehydratase and carbon atoms 2 and 3 are incorporated, as acetyl-CoA, into citrate (C-1,2). The specific activity of carbon atoms 2 and 3 of serine may be obtained directly by the application of the citrate colorimetric assay as a degradation procedure. The error in the determination of the specific activity of the individual carbon atoms of serine is routinely less than 3%. The method may be adapted for the separate analysis of stereoisomeric forms of serine (and other compounds degradable to acetate) in biological materials.

Regulation of the glucolytic enzymes in Pseudomonas putida.

The synthesis of glucose catabolizing enzymes is under inductive control inPseudomonas putida. Glucose, gluconate and 2-ketogluconate are the best nutritional inducers of these enzymes. Mutants unable to catabolize gluconate or 2-ketogluconate synthesized relatively high levels of glucose dehydrogenase and gluconate-6P dehydrase activities when grown in the presence of these substrates. This identifies both compounds as true inducers of these enzymes. KDGP aldolase is induced by its substrate, as evidenced by the inability of mutant cells unable to form KDGP to produce this enzyme at levels above the basal one. A 3-carbon compound appears to be the inducer of glyceraldehyde-3P dehydrogenase. This pattern of regulation suggests that there is a low degree of coordinate control in the synthesis of the glucolytic enzymes byP. putida. This is also supported by the lack of proportionality found in the levels of two enzymes governed by the same inducers, glucose dehydrogenase and gluconate-6P dehydrase, in cells grown on different conditions.

Metabolic interactions of glucose, lactate, and beta-hydroxybutyrate in rat brain slices.

Metabolic interactions of glucose, lactate, and beta-hydroxybutyrate in rat brain slices.

Oxygenation of Unsaturated Fatty Acids by the Vesicular Gland of Sheep

Abstract The products formed on oxygenation of certain unsaturated fatty acids in preparations of sheep vesicular gland have been studied. Oxygenation of linoleic acid yielded 9-hydroxy-10,12-octadecadienoic acid (82%) and 13-hydroxy-9, 11-octadecadienoic acid (18%). Oxygenation of 8,11,14-eicosatrienoic acid yielded 11-hydroxy-8,12,14-eicosatrienoic acid, 15-hydroxy-8,11,13-eicosatrienoic acid, 12-hydroxy-8,10-heptadecadienoic acid, prostaglandin E1 (PGE1), and prostaglandin F1α. The biosynthesis of 12-hydroxy-8,10-heptadecadienoic acid was studied with the use of [2-14C]-, [9-3H,3-14C]-, [10-3H,3-14C]-, [11-3H,2-14C]-, [13d-3H,3-14C]-, [13l-3H,3-14C]-, and [15-3H,3-14C]8,11,14-eicosatrienoic acids. These experiments showed that C-9, C-10, and C-11 are eliminated from the precursor and that the stereochemistry of the removal of hydrogen from C-13 is identical with that occurring during the biosynthesis of PGE1. The 3-carbon compound formed together with 12-hydroxy-8,10-heptadecadienoic acid from 8,11,14-eicosatrienoic acid was identified as malonaldehyde. The identification could be accomplished by condensing malonaldehyde with l-arginine, yielding δ-N-2(pyrimidinyl)-l-ornithine. The mode of formation of 12-hydroxy-8,10-heptadecadie-noic acid and malonaldehyde from 8,11,14-eicosatrienoic acid is discussed. The compounds are proposed to originate in a cyclic peroxide, which has earlier been postulated to be an intermediate in the biosynthesis of prostaglandins.

Hyperglyceridemia induced by glycerol feeding

The currently prevailing opinion is that the endogenous plasma triglycerides have their main if not sole origin in the liver. In the hepatic triglyceride synthesis the precursor fatty acids come chiefly from the body free fatty acid pool and the glycerol moiety is apparently derived both from body free glycerol pool and from the 3-carbon compounds of the glycolysis occuring in hepatic cell. Knowledge of the factors which determine and control the rates of hepatic and plasma triglyceride synthesis is so far very incomplete. One of these factors probably is the plasma free fatty acid level (2) but experience on ethanol-induced fatty liver and hyperglyceridemia (4) as well as on high-carbohydrate diet-induced hyperglyceridemia (7) clearly indicates that the regulatory mechanism must be more complex. In a previous study we suggested that the concentration and synthesis rate of ▪-glycerophosphate in the liver cell or in some of its subcellular fractions might be one of the determinants of triglyceride formation (4). This concept has been supported, in a way, by the recent results of Tzur et al. (6). Since the liver ▪-glycerophosphate content can be raised manifold by administration of glycerol it seemed of interest to study whether the plasma and liver lipid levels are influenced by chronic glycerol feeding in the rat.

Enzymatic Synthesis of S-Sulphocysteine from Thiosulphate and Serine

SULPHATE assimilation in Aspergillus nidulans has been shown to involve a step in which thiosulphate reacts with a 3-carbon compound, probably serine, to form S-sulphocysteine as the immediate precursor of cysteine1–5. However, the enzymatic mechanism involved in this assimilatory step has not yet been elucidated. This communication shows that an enzyme preparation obtained from A. nidulans catalyses the condensation of thiosulphate with serine to form S-sulphocysteine if adenosine triphosphate (ATP) and pyridoxal phosphate are added as cofactors.

STUDIES ON THE METABOLISM OF 1,2-PROPANEDIOL-1-PHOSPHATE

Hanzlik et al. (1) observed the glycogenic action of propylene glycol in rats, and Lindberg (2) has isolated its phosphorylated ester from sea urchin eggs. The latter worker has subsequently demonstrat’ed the presence of 1 ,%propanediol phosphate (PDP) in other t’issues (3). Rudney (4, 5) has suggested that PDP might be an intermediate in the conversion of acetone to “formate” and Cz fragment, while Sakami and Lafaye (6) have suggested that PDP is an intermediate in Ohe metabolism of acetone and a precursor of a 3-carbon compound of the glycolytic cycle. Reports from this laboratory have suggested an alternative pathway of 3-carbon compounds of the glycolytic cycle (7, 8). It appeared to us that PDP might be an intermediate in the alternative pathway suggested by experiments in which slices of heart ventricle anabolizing lactic acid were not inhibited by a concentrat’ion of fluoride sufficient to inhibit enolase. Further, it occurred to us, in view of the recent observations of Harting (9), t,hat PDP might react in the same enzyme systems that normally oxidize cY-glycerophosphate, provided the primary alcohol group is not essential for cr-glycerophosphate dehydrogenase activity. The work reported here demonstrates the oxidation of PDP by a-glycerophosphate dehydrogenase and the removal of the end-product of this oxidation by a further oxidation by addition of a heart muscle extract (10). It has been found that a crystalline preparation of n-glyceraldehyde-3phosphate dehydrogenase will replace the heart’ muscle extract. The data suggest a new series of reactions by which the carbon of PDP might be diverted into pyruvic acid of the glycolytic cycle.

Metabolism of "Sulfapyridine-Fast" and Parent Strains of Pneumococcus Type I

SummaryThe acquisition of “sulfapyridine-fastness” by a strain of pneumococcus Type I is associated with a marked diminution in the production of hydrogen peroxide in cultures of this strain. Cell suspensions of the parent and drug-fast strains dehydrogenate glucose equally well. On the other hand, the acquisition of sulfapyridine-fastness is associated with a marked loss of dehydrogenaseactivity for certain 3-carbon compounds (glycerol, lactate, and pyruvate). When sulfapyridine is added directly to the reacting system the dehydrogenase-activity of the parent cells for the same 3-carbon compounds is likewise much decreased.