In vivo post‐translational processing and subunit reconstitution of cephalosporin acylase from Pseudomonas sp. 130

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Abstract
Cephalosporin acylases are a group of enzymes that hydrolyze cephalosporin C (CPC) and/or glutaryl 7‐amino cephalosporanic acid (GL‐7ACA) to produce 7‐amino cephalosporanic acid (7‐ACA). The acylase from Pseudomonas sp. 130 (CA‐130) is highly active on GL‐7ACA and glutaryl 7‐aminodesacetoxycephalosporanic acid (GL‐7ADCA), but much less active on CPC and penicillin G. The gene encoding the enzyme is expressed as a precursor polypeptide consisting of a signal peptide followed by α‐ and β‐subunits, which are separated by a spacer peptide. Removing the signal peptide has little effect on precursor processing or enzyme activity. Substitution of the first residue of the β‐subunit, Ser, results in a complete loss of enzyme activity, and substitution of the last residue of the spacer, Gly, leads to an inactive and unprocessed precursor. The precursor is supposed to be processed autocatalytically, probably intramolecularly. The two subunits of the acylase, which separately are inactive, can generate enzyme activity when coexpressed in Escherichia coli. Data on this and other related acylases indicate that the cephalosporin acylases may belong to a novel class of enzymes (N‐terminal nucleophile hydrolases) described recently.