The Synthesis of Citrovorum Factor by Leuconostoc mesenteroides P 60

Abstract

SUMMARYWhen incubated with p-aminobenzoic acid, formate and glucose, suspensions of a v k a n t strain of ~o n o s t o c meseWoides strain P 60 formed two factors possessing folk acid activity. One of these factors behaved like rhizopterin in supporting the growth of Streptococczcs faecalis strain R but not of Lactobacillus cmei. The other, like leucovorin, supported the growth of Leucmstoc citrovmrn. The synthesis of 'citrovonun factor' was enhanced 5-to 20-fold by the presence of CO, in the gas phase. Sulphathiazole inhibited the synthesis of both factors, the inhibition being overcome competitively by p-aminobenzoic acid. Leucovorin was destroyed by suspensions of L. msenteroides P60 in phosphate-buffered glucose. The diminution of activity for L. citrovmm (decrease of citrovorum factor) was decreased when the incubation was carried out in a C0,-enriched atmosphere. Ascorbic acid, which behaved similarly to CO, in partially preventing inactivation of leucovorin by suspensions of L. me8Woides P60 variant strain, also increased the synthesis of citrovonun factor from formate and p-aminobenzoic acid and partially satisfied the requirement of the growing L. mesenteroides P60 for COB.

The Synthesis of Serine by Leuconostoc mesenteroides P 60

“…Presumably some fact0 r essential for serine synthesis, be it substrate or enzyme, had been destroyed during this preliminary incubation. Leucovorin, for example, is destroyed under these conditions (Cross, 1960). The ability to form serine was restored when CO, was available.…”

“…The simplest explanation, particularly in the light of evidence to be discussed in the following paper (Cross, 1960), is that C02 does not act as a donor of the @-carbon of serine. It is possible that exogenous CO, acts as a one-carbon donor in the initial stages of growth only until sufficient of some endogenous source of the @-carbon of serine is available.…”

“…Perhaps conditions in these suspensions of pre-incubated organisms more closely paralleled those in cultures of the growing organism. The role of CO, in promoting serine synthesis in suspensions of the organism is examined further in the following paper (Cross, 1960). …”