title: Kinetic study on the reaction mechanism of pantothenase: existence of an acyl-enzyme intermediate and role of general acid catalysis.
abstract: A kinetic study was performed on the reaction mechanism of pantothenase (EC 3.5.1.22) catalyzed hydrolysis of the pantothenic acid. A nonlinear progress curve is derived if the reaction occurs at low buffer concentrations. The nonlinearity is due to partial reversibility of the reaction; an acylenzyme (pantoyl-enzyme) is formed during the reaction, and beta-alanine, the other end product, is able to react with the acyl-enzyme and return back to pantothenate. The dependence of the beta-alanine return reaction on buffer concentration and on pH suggests a general acid catalysis during the reaction. A reaction mechanism is suggested, in which the -NH3+ form of beta-alanine participates in the return reaction, and the deacylation of the acyl-enzyme is acid catalyzed.
mesh_terms: D000215:Acylation; D000409:Alanine / Q000494:pharmacology; D000581:Amidohydrolases / Q000378:metabolism*; D007700:Kinetics; D008433:Mathematics; D010205:Pantothenic Acid; D011485:Protein Binding; D011551:Pseudomonas fluorescens / Q000201:enzymology
chemical_list: D010205:Pantothenic Acid; D000581:Amidohydrolases; C022317:pantothenase; D000409:Alanine