Studies on Microbial Biosynthesis of Pantothenic Acid

Part V. Pantothenate Synthesis from Pantoate and β-Alanine by Escherichia coli Extracts

Abstract

Pantothenate synthesis from pantoate and β-alanine by Escherichia coli extracts was studied as a model synthesis of the peptide bond. It was found as the evidence for occurence of pantoyl-carboxyl activation that a significant quantity of pantoic acid hydroxamate was formed in the reaction mixture containing pantoate and ATP. Formation of pantothenate and development of hydroxamate color from activated pantoate were increased under the anaerobical conditions. Inhibition by -SH reagents and reversal of inhibition by thiol com-pounds are indicative of the evidence for involvement of -SH enzyme in pantothenate syn-thesis and pantoate activation. In view of these results, pantoate activation is formulated as shown in the following two-step reaction:
(1) HS-E+AMP_??_PP_??_PP_??_S•E+AMP
(2) PP_??_S•E+C₅H₁₁O₂•COO^-_??_C₅H₁₁O₂•CO_??_S•E+PP.