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Characterization and Antifungal Activity of Gazyumaru ( Ficus microcarpa ) Latex Chitinases: Both the Chitin-Binding and the Antifungal Activities of Class I Chitinase Are Reinforced with Increasing Ionic Strength

2005; Oxford University Press; Volume: 69; Issue: 4 Linguagem: Inglês

10.1271/bbb.69.811

1347-6947

Toki Taira, Atsuko OHDOMARI, Naoya NAKAMA, Makiko Shimoji, Masanobu Ishihara,

Enzyme Production and Characterization

Three chitinases, designated gazyumaru latex chitinase (GLx Chi)-A, -B, and -C, were purified from the latex of gazyumaru (Ficus microcarpa). GLx Chi-A,-B, and -C are an acidic class III (33 kDa, pI 4.0), a basic class I (32 kDa, pI 9.3), and a basic class II chitinase (27 kDa, pI>10) respectively. GLx Chi-A did not exhibit any antifungal activity. At low ionic strength, GLx Chi-C exhibited strong antifungal activity, to a similar extent as GLx Chi-B. The antifungal activity of GLx Chi-C became weaker with increasing ionic strength, whereas that of GLx Chi-B became slightly stronger. GLx Chi-B and -C bound to the fungal cell-walls at low ionic strength, and then GLx Chi-C was dissociated from them by an escalation of ionic strength, but this was not the case for GLx Chi-B. The chitin-binding activity of GLx Chi-B was enhanced by increasing ionic strength. These results suggest that the chitin-binding domain of basic class I chitinase binds to the chitin in fungal cell walls by hydrophobic interaction and assists the antifungal action of the chitinase.