Partial purification, and some properties and reactivities of cetraxate benzyl ester hydrochloride-hydrolyzing enzyme

Debenzylating enzyme from Aspergillus niger enzyme (commercial crude cellulase) catalyzes the hydrolysis of cetraxate benzyl ester hydrochloride (2), a precursor of the antiulcer agent (1). The enzyme was highly purified by three kinds of chromatographies (hydrophobic, ion exchange, gel filtration) with a recovery of 36%. The content of the debenzylating enzyme was about 0.1% in the crude cellulase, but the enzyme showed no cellulase activity. The purified enzyme was inactivated by Hg2+, and diisopropyl phosphorofluoridate (DFP). It was a monomer with a molecular weight of about 35,000, and its isoelectric point was estimated to be 5.3. It showed a debenzylating activity for the phenylpropionic acid benzyl ester moiety of various benzyl ester derivatives, and the benzyl ester of phenylalanine or that of tyrosine was also well hydrolyzed.