Summary: We have constructed secretion vector plasmids that have unique /II sites within or near the signal sequence of penicillinase, and have also constructed penicillinase cartridges that lack either one, two or three of the processing sites for the membrane-bound, exolarge and exo-small enzymes. Each of these penicillinase cartridges was cloned on secretion vectors in , and enzyme production was examined. The presence of both the signal sequence and the three host-specific processing sites on the secretion vector was required for an effective expression of the enzyme in The presence of any of the processing sites on the cartridge reduced the accumulation of penicillinase in the culture medium. When a vector plasmid lacking part of the hydrophobic region of the signal sequence and lacking the three processing sites was used, total penicillinase production decreased and enzyme accumulation in the medium was extremely low, despite the complete or incomplete presence of the processing sites on the cartridge. Molecular mass determination of these extracellular penicillinases suggested the existence of a new cleavage site for the enzyme.


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