1. Faculty of Education, Kumamoto University, 2-40-1, Kurokami, Kumamoto 860-8555, Japan, Laboratory of Biochemistry, Gifu Pharmaceutical University, 5-6-1, Mitahora-higashi, Gifu 502-8585, Japan, and Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1, Oe-honmachi, Kumamoto 862-0973, Japan