Abstract
It was found that folic acid biosynthesis took place in two steps : first, p-aminobenzoyl-glutamate formation from PABA and L-glutamate, and second, folic acid formation from the formed p-aminobenzoylglutamate and xanthopterin. From experiments using an enzyme treated with ion-exchange resin (IRA-400) it was found that for the peptide formation from PABA and L-glutamate ATP, CoA and Mg ion were required as co-factors, and that by this reaction the equal moles of pyrophosphate and AMP were formed. From the fact that the p-aminobenzoylhydroxamate formation did not decrease in amount by the use of IRA-400 treated enzyme, and also from some other evidences., it was concluded that p-aminobenzoyl-AMP and p-aminobenzoyl-CoA acted as active intermediates in this reaction. The folic acid biosynthesis from p-aminobenzoyl-glutamate and xanthopterin was measured quantitatively with the method of IR-4B fractionation. This enzyme could also be separatd into active apo-enzyme and co-enzyme by the IRA-400 treatment.
