title: Enzymological properties of pantothenate synthetase from Escherichia coli B.
abstract: Following a previous report on physicochemical properties, the enzymological properties of a homogeneously purified preparation of pantothenate synthetase were described. The optimum pH was 10.0 and optimum temperature 30 degrees C. The lyophilized enzyme was very stable on standing at -20 degrees C. K+ or NH4+ and Mg2+ were required as activators; other cations examined were inhibitive to various extents and the enzyme required ATP as the energy supplier. Some omega-amino acids exerted strong inhibition, and the enzyme was inhibited by some chelating agents but was not affected by SH compounds and SH inhibitors. Apparent Km for pantoate was 6.3 x 10(-5)M, for beta-alanine 1.5 x 10(-4)M, and for ATP 1.0 x 10(-4)M. According to the method of Cleland, the enzyme reaction proceeds by a Bi Uni Uni Bi Ping Pong mechanism and a scheme showing the order of binding of substrates and releasing of products is presented.
mesh_terms: D002412:Cations; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D010205:Pantothenic Acid / Q000096:biosynthesis; D010453:Peptide Synthases / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D002412:Cations; D010205:Pantothenic Acid; D010453:Peptide Synthases