期刊名称：Journal of Nutritional Science and Vitaminology
印刷版ISSN：0301-4800
电子版ISSN：1881-7742
出版年度：1976
卷号：22
期号：5
页码：365-373
DOI：10.3177/jnsv.22.365
出版社：Center for Academic Publications Japan
摘要：Dihydrofolate synthetase (EC 6. 3. 2. 12) from Serratia indica IFO 3759 require a divalent cation and a univalent cation for its ac tivity. The divalent cation requirement was satisfied by magnesium ion, manganese ion or ferrous ion. High activity was obtained with 5 mM of magnesium ion. The effect of manganese ion was weak. The univalent cation requirement was satisfied by potassium ion, ammonium ion or rubidium ion, and high activity was obtained with 100 mM of each univalent cation. Increase in the potassium concentration lowered Km values for dihydropteroate and L-glutamate, and raised V max for ATP and dihydropteroate. Potassium ion had little effect on Km value for ATP. These results suggest that potassium ion may function on the affinities of dihydropteroate and L-glutamate to the enzyme. Dihydrofolate synthetase was inhibited by the addition of reduced forms of homopteroic acid. Stronger inhibition was observed by dihydrohomopteroate than by tetrahydrohomopteroate.
