Crystal Structure of Glycyl Endopeptidase from Carica papaya: A Cysteine Endopeptidase of Unusual Substrate Specificity

Citations Over TimeTop 14% of 1995 papers

Abstract

Glycyl endopeptidase is a cysteine endopeptidase of the papain family, characterized by specificity for cleavage C-terminal to glycyl residues only and by resistance to inhibition by members of the cystatin family of cysteine proteinase inhibitors. Glycyl endopeptidase has been crystallized from high salt with a substrate-like inhibitor covalently bound to the catalytic Cys 25. The structure has been solved by molecular replacement with the structure of papain and refined at 2.1 A to an R factor of 0.196 (Rfree = 0.258) with good geometry. The structure of the S1 substrate binding site of glycyl endopeptidase differs from that of papain by the substitution of glycines at residues 23 and 65 in papain, with glutamic acid and arginine, respectively, in glycyl endopeptidase. The side chains of these residues form a barrier across the binding pocket, effectively excluding substrate residues with large side chains from the S1 subsite. The constriction of this subsite in glycyl endopeptidase explains the unique specificity of this enzyme for cleavage after glycyl residues and is a major component of its resistance to inhibition by cystatins.

Related Papers

• → On the active site of proteases. III. Mapping the active site of papain; specific peptide inhibitors of papain(1968)407 cited
• → Oxidized Substrates of APEH as a Tool to Study the Endoprotease Activity of the Enzyme(2021)9 cited
• → Purification and characterization of a novel prolyl endopeptidase from <i>Aspergillus niger</i>(2005)18 cited
• → The activation reaction of papain(1967)74 cited
• The 60Co gamma-radiolysis of aqueous papain solutions: repair and protection by cysteine.(1971)