Stoicheiometry of the citrulline phosphorylase reaction of Streptococcus lactis

Abstract

Further experiments are in progress on the nature of the block in M 97-21, i.e. whether it is lacking an enzyme or is inhibited by a metabolite which it accumulates and which is involved in the valineisoleucine equilibrium. SUMMARY 1. The growth of four mutants of E8cherichia coli requiring L-threonine is inhibited by the presence of L-serine in the culture medium. 2. The inhibition by DL-serine is competitive and is suppressed by D-threonine, a-aminobutyric acid, a-oxobutyric acid, oc-oxo-p-hydroxybutyric acid and L-isoleucine. 3. All the above-listed compounds, except Lisoleucine, exert a sparing effect in the utilization of L-threonine. 4. A mutant requiring either D-threonine, aaminobutyric acid or L-isoleucine is also inhibited by DL-serine, when grown on D-threonine or xaminobutyric acid. 5. These results lead to the hypothesis that Lisoleucine synthesis depends on L-threonine utilization in these mutants.

Galactose transport systems in Streptococcus lactis

“…In practice, the selective generation of either of these two high-energy compounds is difficult to attain since both are produced simultaneously during glycolysis. Recent results obtained in this laboratory (28, 30) have obviated these difficulties: (i) the starved cells of S. lactis were found to maintain an intracellular PEP potential for PTS-mediated sugar transport: and (ii) cells grown previously on galactose were induced for the enzymes of the arginine deiminase pathway (1,13,14,23), and intracellular ATP could thus be generated from the catabolism of arginine (1, 8, 10, 27). The capacity to generate ATP and PEP independently in vivo has permitted kinetic parameters and substrate specificities to be determined for each transport system in physiologically intact cells.…”

The Metabolism Op Ahginine in Serratia Marcescens I. Pathways of Synthesis and Degradation

“…obtained for the participation of inorganic phosphate, ATP, oxygen, or fumarate. The same authors (1952b, 1953), and also Knivett (1952Knivett ( , 1954aKnivett ( , 1954bKnivett ( , 1954c, Korzenovsky andWerkman (1953, 1954), and Slade, Doughty, and Slamp (1954) ..... (3) phosphate ornithine+C0 2 +NH 3 ...... 4--+ * Department of Biochemistry, University of Sydney.…”