Mesorhizobium sp. LUK, which utilizes 3-amino-3-phenylpropionic acid as the sole source of nitrogen with high enantioselectivity (E(S)>100), was isolated using enrichment culture. The enzyme involved in the utilization of (S)-3-amino-3-phenylpropionic acid was confirmed to be a transaminase and was purified by 235-folds with a specific activity of 0.72 U/mg. The molecular weight of the purified protein was ca. 47 kDa and the active enzyme was determined as a dimer on gel filtration chromatography. The N-terminal sequence was obtained from the purified protein. Spontaneous decarboxylation of produced ${eta}-keto$ acids was observed during the chiral resolution of 3-amino-3-phenylpropionic acid.