Two catalytic domains of Chlorella virus CVK2 chitinase.
VChti-1 chitinase encoded by the Chlorella virus CVK2 contained two catalytic domains belonging to family 18 glycosyl hydrolases. The first catalytic domain on a C-terminal-truncated derivative of vChti-1 generated exclusively chitobiose from chitotetraose, chitohexaose, and colloidal high-molecular mass chitin in the enzyme reaction, a typical characteristic of an exochitinase. In contrast, N-acetylglucosamine was produced from chitobiose as well as from chitooligosaccharides by the second catalytic domain on an N-terminal-truncated derivative of vChti-1. Therefore, the second domain possessed N-acetylglucosaminidase activity as well as endochitinase activity. The presence of two catalytic domains with different enzymatic properties in the viral enzyme seems to be necessary for hydrolyzing natural substrates in a cooperative fashion.
Hiramatsu
S
S
Department of Molecular Biotechnology, Graduate School of ADSM, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan.
Fujie
M
M
Usami
S
S
Sakai
K
K
Yamada
T
T