Crystalline mammalian L-amino acid oxidase from rat kidney mitochondria.

L-Amino acid oxidase has been crystallized from extracts of rat kidney mitochondria. Purification involved sonic extraction, ammonium sulfate fractionation, chromatography on diethylaminoethyl cellulose, and gel filtration through Sephadex G-ZOO. The enzyme revealed a single protein band on starch gel electrophoresis and exhibited a single homogeneous peak (a%, W = 10.5 S) in an ultracentrifuge. The enzyme is a flavoprotein in which the prosthetic group appears to be flavin mononucleotide. On the basis of the flavin mononucleotide content of the enzyme (0.92 %) and its molecular weight (88,900 =t l,lOO), it has been concluded that the enzyme contains 2 moles of flavin mononucleotide per mole. The enzyme catalyzes the oxidation of many ol-aminomonocarboxylic and a-hydroxy acids (L configuration) but has no action on optically inactive acids such as glycine and or-hydroxyisobutyric acid. The turnover numbers for the oxidation of L-leucine and of L-lactic acid were 6.3 and 26 moles per min per mole of flavin mononucleotide conjugated with enzyme, respectively.