title: Characterization and inhibition of dihydrofolate synthetase from Neisseria gonorrhoeae.
abstract: Dihydrofolate synthetase (EC 6.3.2.12) from N. gonorrhoeae was isolated and enzyme characteristics were determined. The purified enzyme was found quite stable when stored at -60 degrees C. About 50% of the enzyme activity was destroyed within 6 weeks when kept at 4 degrees C. Maximum velocity was observed at pH 9.3. The enzyme required a monovalent cation, K+ or NH4+, and divalent cation, Mg2+ or Mn2+, for its function. ATP at 5 mM concentration gave maximum activity. Km values for dihydropteroate and L-glutamate at pH 9.3 were 3.5 X 10(-5) M and 6.5 X 10(-4) M, respectively. Patterns of product inhibition by dihydrofolate were found to be non-competitive with respect to dihydropteroate, having a Ki value of 5.1 +/- 0.8 X 10(-4) M, and competitive with respect to L-glutamate, having a Ki value of 6.2 X 10(-4) M.
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology; D002414:Cations, Monovalent / Q000494:pharmacology; D007700:Kinetics; D009344:Neisseria gonorrhoeae / Q000187:drug effects / Q000201:enzymology*; D010453:Peptide Synthases / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000302:isolation & purification
chemical_list: D000227:Adenine Nucleotides; D002413:Cations, Divalent; D002414:Cations, Monovalent; D010453:Peptide Synthases; C020041:dihydrofolate synthetase