The Hydrolysis of Mono-, Di-, and Triglutamate Derivatives of Folic Acid with Bacterial Enzymes

A soil organism of the genus Flavobacterium was isolated from a medium containing folic acid as the sole source of carbon and nitrogen (ATCC 25012). This organism resembles but is not identical with a previously described strain, Flavobacterium polyglutamicum. It utilizes the glutamate released from pteroylmonoglutamate by the action of an intracellular enzyme, folate amidase. The relative rates of enzymatic hydrolysis of a variety of analogues of pteroylmonoglutamate were determined in order to characterize the substrate specificity of folate amidase. Gel filtration was used to separate folate amidase from two other bacterial enzymes: one that acts on α-glutamylglutamate and another that splits γ-glutamylglutamate. Enzyme fractions that hydrolyzed γ-glutamylglutamate also released free glutamate from pteroyl-γ-diglutamate and pteroyl-γ,γ-triglutamate.