Factors Influencing Conversion of Folic Acid to Citrovorum Factor by Chick Liver Fractions.

Abstract

The presence in rat and chick liver of an enzyme system converting pteroylglutamic acid (PGA) to citrovorum factor (CF) has been reported. The importance of this enzyme system has become evident in recent years in that reports have appeared indicating a probable CF-catalyzed utilization of formate in synthesis of purines. The present report concerns the study of factors affecting PGA to CF conversion by the chick liver fractions. Chick liver was fractionated into supernatant, acetone powder, 15% and 40% alcohol precipitated fractions and dialyzed supernatant. The supernatant fraction of chick liver is the principal source of the PGA to CF converting enzyme. The latter is precipitated by 40% alcohol and by 66% acetone. Addition of homocysteine consistently enhances PGA to CF conversion by the chick liver fractions. The enzymatic synthesis of CF from PGA is optimal in the presence of homocysteine, serine and Mg++. Under these conditions the glycine content of the acetone powder is increased 4-fold.