A process for producing L- beta -chloroalanine or L- beta -bromoalanine, which comprises bringing 3-chloro-2-ketobutyric acid or 3-bromo-2-ketobutyric acid as a substrate into contact with an active substance capable of asymmetrically reducing and aminating 2-ketobutyric acid in the presence of the reduced form nicotinamide-adenine-dinucleotide (NADH) and an ammonia source. Examples of the active substance include those having alanine dehydrogenase, leucine dehydrogenase and phenylalanine dehydrogenase activities. If necessary, the above process may incorporate an NADH regenerating system.
