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°C. The lyophilized enzyme was very stable on standing at -20°C. K+ or NH4+ and Mg2+ or Mn2+ were required as activators; other cations examined were inhibitive to various extents and the enzyme required ATP as the energy supplier. Some co-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 6.3×10-5M, for β-alanine 1.5×10-4 M, and for ATP 1.0×10-4M, 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.
