Characterization of proteolytic activity associated with<i>Bacillus thuringiensis</i>var.<i>darmstadiensis</i>crystals

Abstract

14C-labelled Bacillus thuringiensis var. darmstadiensis (Btd) crystals were used to detect crystal-associated protease activity. Optimal protease activity occurred at pH 8.4 and 9.7, and at 15 and 35°C. Protease activity was destroyed by heating the crystals at 121°C for 15 min. Cellular enzymes from Btd did not solubilise Btd crystals. Iodoacetic acid (50 mM) caused a 20% reduction in protease activity while phenylmethyl-sulphonylfluoride (PMSF), ethylenediamine-tetraacetic acid (EDTA) and p-chloromercuribenzene (PCMB) had no inhibitory effect on protease activity.