Comparison of phytolacain G, a cysteine protease from fruit of Phytolacca americana, with phytolacain R.
The enzymatic properties of phytolacain G, a protease isolated from green fruit of pokeweed, were compared with those of phytolacain R, a protease obtained from ripe fruit. The optimum pH of phytolacain G was 7.5-8.0 at 37 degrees C using casein as the substrate. The enzyme was strongly inhibited by iodoacetic acid and p-chloromercuribenzoic acid, but not by diisopropyl fluorophosphate or EDTA. These results indicated that phytolacain G was a cysteine protease, like phytolacain R. Nine sites of oxidized insulin B-chain were cleaved by phytolacain G during 20 h of hydrolysis. The six sites cleaved by phytolacain G were also cleaved by phytolacain R. The substrate specificity of phytolacain G was broad, but the preference for hydrophobic residues at the P2 position was similar to the substrate specificity of papain. The amino-terminal sequence of phytolacain G was not identical with that of phytolacain R; however, the amino acid residues conserved in the papain family were also conserved in this enzyme.
Uchikoba
T
T
Department of Chemistry, Faculty of Science, Kagoshima University, Japan.
Yonezawa
H
H
Shimada
M
M
Kaneda
M
M
D000595:Amino Acid Sequence; D003546:Cysteine Endopeptidases / Q000737:chemistry*; D005638:Fruit / Q000201:enzymology*; D006801:Humans; D008969:Molecular Sequence Data
D003546:Cysteine Endopeptidases; C116231:phytolacain G; C095519:phytolacain R