The Synthesis of Serine by Leuconostoc mesenteroides P 60

Abstract

SUMMARYThough CO, is essential for the growth of Leuconostoc mesenteroides strain PSO in the absence of serine, WO, is not incorporated into serine by the growing organism. The synthesis of serine was further studied by using suspensions of a variant strain of L. mesenteroides PSO which formed serine more actively than the parent strain. Glycine, formate, glucose, p-aminobenzoic acid and pyridoxal were required for the synthesis of serine by these suspensions. There was an additional requirement for CO, only when the organisms had been incubated previously in phosphate-buffered glucose. Leucovorin satisfied the requirement for both CO, and p-aminobenzoic acid.

The Synthesis of Citrovorum Factor by Leuconostoc mesenteroides P 60

“…When medium L was supplemented with lO-*M-DL-serine no such stimulation occurred. p-Aminobenzoic acid is also required for the synthesis of serine (Cross, 1960), and these factors are formed concurrently with serine when glycine and pyridoxal are also provided. Though some form of folk acid is clearly required for serine synthesis 124…”

“…Carbon dioxide has the dual capacity of stimulating serine synthesis (Lascelles et al 1954;Cross, 1960) and of preventing leucovorin inactivation by Leuconostoc mesenteroides P 60. Any hypothesis about a relationship between these two activities would be supported if another compound which produced one of the phenomena also produced the other.…”

“…For best activity the organisms for suspension were harvested after 10-11 hr. as previously described (Cross, 1960). The supernatant fluids from suspensions of the variant strain in solution D incubated in N, (which contained serine and a little citrovorum factor) were also active in supporting the growth of S. faecalis R, and in replacing pteroylglutamic acid 120…”

“…The complete solution for the synthesis of citrovorum factor normally contained: glucose, 1 0 -2~; sodium formate, 1 0 -,~; p-aminobenzoic acid, 1 0 4~; phosphate buffer, pH 6.9, 1 0 2~-In some experiments, in which the synthesis of serine and citrovorurn factor were being observed concurrently, the reaction mixture (solution D ) also contained : glycine, 2 x 1 0 -2~ and pyridoxal, 1 0 -6~ (Cross, 1960). Modifications in particular experiments are noted in the text.…”

“…In experiments in which the organisms were incubated in 2 x 10-2M-glucose and 10-1 M-phosphate buffer (pH 6-9) before testing their synthetic ability, the procedure was again exactly as previously described (Cross, 1960).…”