1. Faculty of Pharmacy, Meijo University, Tempaku, Nagoya 468-8503, Japan, Department of Applied Chemistry and Microbiology, P.O. Box 56, Viikki Biocenter, FIN-00014, University of Helsinki, Finland, and Central Research Laboratories, Ajinomoto Co., Inc., 1-1 Suzuki-cho, Kawasaki 210-8681, Japan