PRIMARY STRUCTURE OF CC-III, THE GLYCOSYLATED CYSTEINE PROTEINASE FROM THE LATEX OF CARICA-CANDAMARCENSIS HOOK

The amino acid sequence of the cysteine proteinase CC-III from the lat ex of the subtropical species Carica candamarcensis Hook has been dete rmined with the exception of seven residues (pos. 180-186). It was ded uced from the sequence analysis of the whole chain and peptides obtain ed by tryptic, chymotryptic, peptic and thermolysinolytic hydrolysis. CC-III consists of 214 amino acid residues. Out of a total of eight cy steine residues, six are located at positions involved in the formatio n of the three disulfide bridges stabilizing the structure of papain r elated enzymes. CC-III from Carica candamarcensis is a glycoprotein wi th the carbohydrate moiety bound to asparagine at position 44. Out of 210 residues compared with the sequences of the four cysteine proteina ses of Carica papaya L., CC-III shares 125 identical ones (59.5%) with papain, 142 (67.6%) with papaya proteinase IV, 146 (69.5%) with papay a proteinase III and 156 (74.3%) with chymopapain. All amino acid resi dues constituting the active site and subsite S2 in chymopapain are co nserved in CC-III with the exception of the substitution Leu(157)--> V al in the latter. This fact as well as the highest degree of identity between CC-III and chymopapain point to a similar specificity of both enzymes and thus CC-III might be a suitable substitute for chymopapain as a chemonucleolytic agent.