Isolation and primary structure of the CCI papain-like cysteine proteinases from the latex of Carica candamarcensis Hook

The dried latex of the mountain papaya, Carica candamarcensis, was chromato graphed on CM-Sephadex C50, giving rise to three peaks (CCI, CCII and CCIII ) with amidase activity on N-alpha-benzoyl-DL-arginine-4-nitroanilide. The less basic, most active, peak, CCI, was separated into two components, CCIa and CCIb, by reverse-phase HPLC under denaturing conditions. The primary s tructures of CCIa and CCIb are presented, They were deduced from sequence a nalysis of the whole proteins and peptides resulting from enzymatic digesti ons. Both proteinases are made of 213 amino acid residues, CCIb sharing 88- 89% similarity with the three subvariants (G(90)/R-212, E-90/R-212, E-90/K- 212) Of CCIa. 139-140 amino acid residues (65.8%) of CCIa and 141 residues (66.5%) of CCIb are common to papain, The seven cysteine residues are align ed with those of papain and the catalytic triad (Cys(25), His(159) Asn(175) ) Of all cysteine peptidases of the papain family is conserved. The similar ity with the other cysteine proteases from Carica papaya is discussed.