1. Chemistry Research Laboratories, Pharmacology and Microbiology Research Laboratories, Dainippon Pharmaceutical Co., Ltd., 33-94, Enoki, Suita, Osaka 564-0053, Japan, Department of Bioengineering, Tokyo Institute of Technology, 4259, Nagatsuda, Midori-ku, Yokohama 226-8501, Japan, and Department of Biological Chemistry, Chubu University, 1200 Matsumoto, Kasugai, Aichi 487-8501, Japan