title: Alanine racemase of alfalfa seedlings (Medicago sativa L.): first evidence for the presence of an amino acid racemase in plants.
abstract: We demonstrated several kinds of D-amino acids in plant seedlings, and moreover alanine racemase (E.C.5.1.1.1) in alfalfa (Medicago sativa L.) seedlings. This is the first evidence for the presence of amino acid racemase in plant. The enzyme was effectively induced by the addition of L- or D-alanine, and we highly purified the enzyme to show enzymological properties. The enzyme exclusively catalyzed racemization of L- and D-alanine. The K(m) and V(max) values of enzyme for L-alanine were 29.6 x 10(-3) M and 1.02 mol/s/kg, and those for D-alanine are 12.0 x 10(-3) M and 0.44 mol/s/kg, respectively. The K(eq) value was estimated to be about 1 and indicated that the enzyme catalyzes a typical racemization of both enantiomers of alanine. The enzyme was inactivated by hydroxylamine, phenylhydrazine and some other pyridoxal 5'-phosphate enzyme inhibitors. Accordingly, the enzyme required pyridoxal 5'-phosphate as a coenzyme, and enzymologically resembled bacterial alanine racemases studied so far.
authors.affiliation: Department of Biotechnology, Faculty of Engineering, Kansai University, Suita-Shi, Osaka-Fu, Japan.
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Ono
authors.forename: Kazuki
authors.initials: K
authors.lastname: Yanagida
authors.forename: Tadao
authors.initials: T
authors.lastname: Oikawa
authors.forename: Tadashi
authors.initials: T
authors.lastname: Ogawa
authors.forename: Kenji
authors.initials: K
authors.lastname: Soda
mesh_terms: D000409:Alanine / Q000737:chemistry; D000411:Alanine Racemase / Q000737:chemistry*; D002240:Carbohydrate Sequence; D000455:Medicago sativa / Q000737:chemistry* / Q000201:enzymology*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D036226:Seedlings / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000411:Alanine Racemase; D000409:Alanine