1. Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151-747, Korea, Department of Clinical Pathology, Catholic University Medical College, Seoul, Korea, Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, 06080 Badajoz, Spain, and Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164