ARGININE METABOLISM IN PLEUROPNEUMONIA-LIKE ORGANISMS ISOLATED FROM MAMMALIAN CELL CULTURE

Schimke, Robert T. (National Institutes of Health, Bethesda, Md.) and Michael F. Barile. Arginine metabolism in pleuropneumonia-like organisms isolated from mammalian cell culture. J. Bacteriol. 86:195-206. 1963.-Arginine degradation is a significant metabolic process for pleuropneumonia-like organisms (PPLO; Mycoplasma) isolated from cell culture. The conversion of arginine to ornithine in PPLO-contaminated cell culture was rapid, and occurred by the arginine dihydrolase pathway involving arginine deiminase, ornithine transcarbamylase, and carbamyl phosphokinase. In the absence of PPLO contamination, arginine conversion to ornithine was minimal and took place by an arginase activity present in the cell culture, but not in the PPLO. All five PPLO strains isolated from cell culture accomplished the conversion of arginine to ornithine, and contained the requisite enzyme of the arginine dihydrolase system, whereas PPLO-free cell cultures did not. Supplementation of PPLO culture broth with arginine increased the extent of PPLO growth. When the arginine content of the culture limited growth, arginine was completely converted to ornithine. When growth was limited in the presence of excess arginine, citrulline was the major breakdown product. It is suggested that the conversion of arginine to ornithing constitutes a significant, and possibly major, source of adenosine triphosphate for this class of organisms.

EFFECTS OF EXERCISE AND ADMINISTRATION OF ASPARTIC ACID ON BLOOD AMMONIA IN THE RAT

The rise of blood ammonia following a short period of exercise can be partially prevented by the prior oral administration of either aspartic acid or the mixed potassium and magnesium salts of aspartic acid. These compounds will also prolong the time required for the rat to reach physical exhaustion due to forced swimming. As an extension of these observations, it has been found that daily feeding of ammonium carbonate over a 4-week period will also prevent the rise of blood ammonia due to exercise and will prolong exhaustion time of rats that are forced to swim. These same changes have been observed in rats that were exercised daily by short periods of forced swimming and, after 3 weeks of this type of physical training, were tested for blood ammonia response to exercise and time required for exhaustion. It is concluded that both daily ammonium carbonate feeding and training result in adaptation of enzymes in the ornithine cycle so as to increase the rate of blood ammonia removal.

CONTROL OF URACIL SYNTHESIS BY ARGININE IN ESCHERICHIA COLI

Ben-Ishai, Ruth (Israel Institute of Technology, Haifa), Michal Lahav, and Ada Zamir. Control of uracil synthesis by arginine in Escherichia coli. J. Bacteriol. 87:1436-1442. 1964.-It is shown that arginine affects uracil biosynthesis in Escherichia coli. The effect of arginine on uracil synthesis was analyzed by following the changes in the level of aspartate transcarbamylase, the first specific enzyme in uracil synthesis. In this research, an effect of arginine on aspartate transcarbamylase formation was observed only if the bacteria were preincubated with arginine in the presence of uracil analogues that cause apparent partial derepression of this enzyme. The possible effect of a structural modification of aspartate transcarbamylase by 2-thiouracil, the analogue principally used, is considered. However, it is shown that arginine causes derepression of aspartate transcarbamylase, even if a modification of the enzyme occurs. An effect of uracil on arginine synthesis can also be observed in repressible strains of E. coli, if conditions of partial derepression of the enzymes involved in arginine synthesis prevail. However, neither the derepression of aspartate transcarbamylase by arginine nor the derepression of ornithine transcarbamylase by uracil is accompanied by changes in the level of carbamyl phosphokinase, the enzyme that catalyzes carbamyl phosphate synthesis.

THE ISOLATION OF AMINO ACIDS FROM MIXTURES AS THEIR N-2,4-DINITROPHENYL DERIVATIVES, METHIONINE, LEUCINE, PHENYLALANINE, ORNITHINE, LYSINE AND TYROSINE

1. The separation of the dinitrophenyl derivatives of methionine, leucine (together with isoleucine), phenylalanine, ornithine, lysine and tyrosine from each other, and from the dinitrophenyl derivatives of the other protein amino acids, by partition chromatography on columns is described. 2. The harmful effect on resolving power of using too close-fitting a packing tool in preparing these partition columns is indicated and the dimensions needed to obtain good resolution are given.

THE BIOSYNTHESIS OF GRAMICIDIN S IN A CELL-FREE SYSTEM

1. A cell-free system prepared from Bacillus brevis cells, harvested in the late phase of growth and consisting of the 11000g supernatant, has been shown to incorporate into gramicidin S the five constituent amino acids added in labelled form. The results are consistent with complete synthesis and not merely a completion of pre-existing intermediate peptides. 2. The incorporation of (14)C-labelled amino acids by the 11000g supernatant into gramicidin S requires an energy source. Omission of phosphoenolpyruvate and pyruvate kinase from the incubation mixture prevents incorporation into gramicidin S. The cell-free system incorporates [(14)C]-leucine, -proline and -phenylalanine over a period of 4hr. With [(14)C]leucine, incorporation into gramicidin S takes place in the range pH6-9 with maximum incorporation at pH7.0. High concentrations of chloramphenicol or puromycin decreased the incorporation into gramicidin S by only about 20%. 3. The 50000g supernatant exhibited no decrease in ability of incorporating [(14)C]valine into gramicidin S as compared with the 11000g supernatant. About 40% of the incorporating ability remained in the 105000g supernatant after 3hr. centrifugation. When recombining the 105000g sediment with the 105000g supernatant, some increase in incorporation over that obtained with the supernatant alone was obtained. The findings tend to support the view that gramicidin S is synthesized in a different manner from that of proteins.

OXAMIC TRANSCARBAMYLASE OF STREPTOCOCCUS ALLANTOICUS

Bojanowski, R. (University of Illinois, Urbana), Elizabeth Gaudy, R. C. Valentine, and R. S. Wolfe. Oxamic transcarbamylase of Streptococcus allantoicus. J. Bacteriol. 87:75-80. 1964.-An improved colorimetric assay for carbamyl oxamate, which allows the precise measurement of the activity of oxamic transcarbamylase, has been developed. Activity is maximum over the pH range from 8.3 to 8.7. A cation requirement is satisfied by 2.5 x 10(-3)m Mg(++) or Mn(++). The equilibrium constant for the phosphorolysis of carbamyl oxamic acid is 1.6, corresponding to a negative free energy change of -285 cal per mole.

PHYSIOLOGY OF THE SPORULATION PROCESS IN CLOSTRIDIUM BOTULINUM. II. MATURATION OF FORESPORES

Day, Lawrence E., (Michigan State University, East Lansing) and Ralph N. Costilow. Physiology of the sporulation process in Clostridium botulinum. II. Maturation of forespores. J. Bacteriol. 88:695-701. 1964.-Clostridium botulinum, strain 62-A, did not sporulate endotrophically, but forespores matured to refractile, heat-resistant spores when replaced in solutions containing l-alanine and l-proline, l-isoleucine and l-proline, or l-alanine and l-arginine. Solutions of l-arginine or l-citrulline would not support the maturation process. Acetate, CO(2), and delta-amino valeric acid were produced during sporulation in a replacement solution of l-alanine and l-proline, indicating the operation of the Stickland reaction. There was no large uptake of either exogenous l-alanine or acetate during this process. Similarly, there was no apparent protein or nucleic acid synthesis, since high levels of chloramphenicol, 8-azaguanine, or mitomycin C failed to inhibit, and no significant amount of P(32) was incorporated into the spore nucleic acids. Dipicolinic acid (DPA) was synthesized during forespore maturation. It is believed that these final steps in sporulation of C. botulinum require only an exogenous source of energy which can be obtained via the Stickland reaction system, and that the synthesis of DPA and other unknown materials relies primarily on endogenous substrates.