Purification and Characterization of Two Chitinase Isoforms from the Bulbs of Gladiolus (Gladiolus gandavensis)
Yamagami, Takeshi | Mine, Yoichiro | Aso, Yoichi | Ishiguro, Masatsune
Two chitinase isoforms, designated GBC-a and GBC-b, were purified from the bulbs of gladiolus (Gladiolus gandavensis) using CM-cellulose column chromatography followed by Butyl-Toyopearl 650M hydrophobic column chromatography, gel filtration on Sephadex G-75, and Mono-S FPLC. GBC-a and GBC-b are weakly acidic and weakly basic proteins with molecular masses of 30 kDa, and isoelectric points of 6.0 and 7.5, respectively. GBC-a and GBC-b were found to be homologous proteins with similar amino acid compositions and N-terminal sequences. The number of half-cystine residues in GBC-a and GBC-b was only one each, which is much lower than those of plant class I (15–17 Cys residues/mol), class II (5–8 Cys residues/mol), and class III (6 Cys residues/mol) chitinases. The N-terminal sequences of GBC-a and GBC-b were completely different from those of plant three classes of chitinases. The optimal pHs of these chitinases toward glycolchitin were pH 5. GBC-a hydrolyzed (GlcNAc)₆ into (GlcNAc)₂, (GlcNAc)₃ and (GlcNAc)₄, and (GlcNAc)₅, into (GlcNAc)₂, and (GlcNAc)₃.
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