The incorporation of formate-C14 into citrovorum factor.

Jukes (1) and Broquist et al. (2) reported that the addition of formate or serine to incubating cells of an A-Methopterin-resistant strain of Xtreptococcus.faecalis increased the amount of citrovorum factor (CF, folinic acid) which was formed from pteroylglutamic acid (PGA). This finding suggested that ‘Lformate-carbon” was incorporated into the structure of CF. Under appropriate conditions an excellent yield of CF is obtainable (3), so that an isolation of CF from bacterial suspensions incubated with PGA is feasible. It is the purpose of this paper to report the preparation of labeled CF which was derived enzymatically from synthetic pteroylglutamic acid and formate-CY4.