[Penicillin acylase from Escherichia coli: catalytically active subunits].

Gel filtration under denaturing conditions was used to isolate the alpha- and beta-subunits of penicillin acylase (PA). Refolded subunits were obtained through removing urea by dialysis. Both renatured subunits were catalytically active during hydrolysis of phenylacetic acid p-nitroanilide; this activity decreased after addition of a serine-specific inhibitor--phenylmethanesulfonyl fluoride. The subunits were also active in reversed micelles of Aerosol OT (AOT) in octane, the optimum hydration degree being 11.9 and 17.5 for the light (alpha) and heavy (beta) subunits, respectively. The positions of the maxima were consistent with both theoretically calculated optimum hydration degrees and the earlier reported profile of enzymatic activity for native PA in reversed micelles.