Tetrahydrofolate-dependent Enzyme Activities of Erythrocytes in Formiminotransferase Deficiency Syndrome

Tetrahydrofolate-dependent enzyme activities were investigated upon erythrocyte lysates from two cases with formiminotransferase deficiency syndrome. The activities of both N5, 10-methylene-tetrahydrofolate dehydrogenase and serine-hydroxymethylase were found to be slightly increased. Cyclohydrolase and formate-activating enzyme were found to be normal in their activity. The results obtained suggested that a metabolic pathway of tetrahydrofolates, including tetrahydrofolate→N5, 10-methylene-tetrahydrofolate→N5, 10-methenyl-tetrahydrofolate→N10-formyltetrahydrofolate, was of an increased activity in erythrocytes in which formiminotransferase was of defective activity.