Specificity of a cysteine proteinase of Entamoeba histolytica towards the alpha 1-CB2 peptide of bovine collagen type I.

The cysteine proteinase of Entamoeba histolytica was shown to hydrolyze the cyanogen bromide peptide alpha 1-CB2 of calf skin collagen type I yielding two split products. Amino acid analyses of the formed peptides and estimation of the amino-terminal residues revealed that the alpha 1-CB2 peptide was exclusively cleaved between Gly10 and Leu11 within the sequence -Arg9-Gly10-Leu11-yielding two peptides with 7 and 29 amino acids, respectively. Under identical conditions the ratio of hydrolysis of the Gly10-Leu11 bond in the alpha 1-CB2 peptide to the Gly23-Phe24 bond within the internal sequence -Arg22-Gly23-Phe24- of bovine insulin B-chain was 100:65. The enzyme was found to split both benzyloxycarbonyl-Arg-Arg-methoxy-2-naphthylamide and benzyloxycarbonyl-Arg-Gly-2-naphthylamide. The ratio of hydrolysis of these substances was 100:11.6. Benzyloxycarbonyl-Gly-Arg-2-naphthylamide was a very poor substrate for the enzyme.