| Abstract: | Saline-washed cells of Bacillus licheniformis strain 749/C (constitutive for penicillinase) were able to release exopenicillinase in the presence of concentrations of chloramphenicol that prevented protein synthesis completely. The release reaction was strongly pH-dependent, occurring at a faster rate at alkaline pH in anionic or cationic buffers than at neutral pH. A strongly pH-dependent release reaction was noted in growing cells also. The reaction in washed cells can be stopped completely by changing the pH to 6.0. Within 30 min at pH 9.0, about 55% of the cell-bound penicillinase was released; thereafter, release continued at a greatly reduced rate. Suspensions of washed cells retained their capacity to release penicillinase at pH 9.0 for 90 min. Penicillinase released at pH 9.0 from either cells or protoplasts was not readsorbed over a 60-min period after changing the pH to 6.0. The release reaction was strongly temperature-dependent. We examined the effect of a large number of metabolic inhibitors and other compounds on the pH-dependent release phenomenon. Quinacrine hydrochloride, chloroquine diphosphate, and chlorpromazine hydrochloride reduced secretion substantially at 10(-4)m. Deoxycholate and Triton X-100 were active at 10(-3)m, but tungstate, arsenate, and molybdate had small effects at 10(-1)m. The rate of exopenicillinase release at pH 9.0 from fully stabilized protoplasts was one-half that of intact cells. Protoplasts lysed in hypotonic media or detergents showed even greater reduction in releasing activity. Penicillinase released from washed cells at pH 7.5 or 9.0 appeared to be derived from the periplasmic tubule and vesicle fraction that was released by protoplast formation. |
