Characterization of the carboxypeptidase N secreted by Hep G2 cells |
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Authors: | B G Grimwood T H Plummer A L Tarentino |
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Affiliation: | Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509. |
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Abstract: | Human hepatoma (Hep G2) cells secrete nanogram quantities of carboxypeptidase enzymes which are capable of hydrolyzing COOH-terminal lysine and arginine residues. A carboxypeptidase with a neutral pH optimum (greater than pH 7.0) was partially purified from the conditioned medium and compared with pure plasma carboxypeptidase N. The two enzymes behaved in a similar manner on gel filtration (apparent Mr = 280,000), DE52 ion exchange chromatography, and concanavalin A-affinity chromatography and were indistinguishable enzymatically and immunologically. Immunoblots of the Hep G2 and plasma carboxypeptidase N before and following deglycosylation with peptide-N4-[N-acetyl-beta-glucosaminyl]asparagine amidase F revealed a similar, if not identical, multimeric structure. A second carboxypeptidase with a lower molecular weight and a pH optimum of 5.0 was also detected in the Hep G2 medium. |
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