Characterization of alpha-glucosyltransferase from Pseudomonas mesoacidophila MX-45.

alpha-Glucosyltransferase was purified from Pseudomonas mesoacidophila MX-45. The molecular weight was estimated to be 63,000 by SDS-PAGE, and the isoelectric point was pI 5.4. For enzyme activity based on sucrose decomposition, the optimum pH and the optimum temperature were pH 5.8 and 40 degrees C, respectively. The ranges of stable pH and temperature were pH 5.1-6.7 and below 40 degrees C, respectively. The purified enzyme of MX-45 converted sucrose into trehalulose (1-O-alpha-D-glucopyranosyl- D-fructose) and isomaltulose (palatinose, 6-O-alpha-D-glucopyranosyl-D-fructose) simultaneously, and the ratio of trehalulose to isomaltulose increased at lower reaction temperatures. Therefore, optimum conditions for trehalulose production were pH 5.5-6.5 at 20 degrees C. The yield of trehalulose from sucrose (20-40% solution) was 91%. The Km for sucrose was 19.2 +/- 3.3 mM estimated by the Hanes-Woolf plot. Product inhibition was observed, and the product inhibition constant was 0.17 M. Hg2+, Fe3+, Cu2+, Mg2+, Ag+, Pb2+, glucono-1,5-lactone, and Tris(hydroxymethyl)aminomethane inhibited the reaction.