THERMOPHILIC AMINOPEPTIDASES FROM BACILLUS STEAROTHERMOPHILUS. I. ISOLATION, SPECIFICITY, AND GENERAL PROPERTIES OF THE THERMOSTABLE AMINOPEPTIDASE I *

摘要: A thermostable aminopeptidase (AP 1) from homogenates of B. stearothermo-philus was purified by filtration on Sephadex G-150, heat treatment, chromatography DEAE and G-200, preparative polyacrylamide gel electrophoresis. The enzyme shows one band in electrophoresis has a pH optimum between 7.5 8 for LNA 9.2 9.4 Gly-Leu-Tyr. One striking feature the amino-acid composition AP I comparison with data leucinaminopeptidase is larger proportion hydrophobic residues glycine. As regards its specificity, differs other amino-peptidases certain important respects. activation energy hydrolysis Leu-Gly calculated to be 16,300 cal/M-1. remains stable several hours at 80 C; after 30 min this temperature activity increases about 20 per cent (Vm increases, while Km same). stability urea, dodecyl sulphate, various alcohols studied. even 10 tertiary butanol, same way as treatment kinetics increase following or butanol are discussed. At 20°C, exhibits sigmoidal dependence reaction velocity concentration whereas 40°C 80°C curves show hyperbolic behaviour. In metal-enzyme complex Co2+ ions strongly bound (up 10-2MEDTA). lower than 6 apo-enzyme formed 10-2M EDTA. can reactivated holo-enzyme adding Co-2. complexes metals different substrate specificities.