Nutritional requirements for folate compounds and some enzyme activities involved in the folate biosynthesis.

Dihydrofolate synthetase activity is widely distributed in various microorganisms and mushrooms. Animals and microorganisms i.e., rat and chicken (in the liver), L. casei and P. cerevisiae, which require essentially pteroylglutamic acid as a nutrient for growth showed no detectable dihydrofolate synthetase activity. S. faecalis R, which can replace pteroylglutamic acid with pteroic acid as a nutrient for growth, had little dihydropteroate synthetase activity but showed normal dihydrofolate synthetase activity. This suggests that the nutritional requirements for folate compounds shown in vivo is in good agreement with the results obtained with dihydropteroate and dihydrofolate synthetase activities in vitro, and that the pathway through dihydropteroic acid as an intermediate is the main route in folate biosynthesis in nature.