The Complete Amino Acid Sequence of Chitinase-B from the Leaves of Pokeweed (Phytolacca americana)

Abstract

The complete amino acid sequence of pokeweed leaf chitinase-B (PLC-B) has been determined by first sequencing all 19 tryptic peptides derived from the reduced and S-carboxymethylated (RCm-) PLC-B and then connecting them by analyzing the chymotryptic peptides from three fragments produced by cyanogen bromide cleavage of RCm-PLC-B. PLC-B consists of 274 amino acid residues and has a molecular mass of 29, 473 Da. Six cysteine residues are linked by disulfide bonds between Cys20 and Cys67, Cys50 and Cys57, and Cys159 and Cys188. From 58-68% sequence homology of PLC-B with five class III chitinases, it was concluded that PLC-B is a basic class III chitinase.