title: Characterization and expression of L-amino acid oxidase of mouse milk.
abstract: l-Amino acid oxidase (LAO) was purified from mouse milk. LAO reacted with l-amino acids in an apparent order of Phe > Met, Tyr > Cys, Leu > His other 11 amino acids tested and produced H(2)O(2) in a dose- and time-dependent manner. LAO in milk had a molecular mass of about 113 kDa and was converted to a 60-kDa protein by SDS-PAGE. LAO consisted of two subunits. The N- and C-terminal amino acid sequence determination followed by cDNA cloning showed that the 60-kDa protein consisted of 497 amino acids. LAO mRNA spanned about 2.0 kb, and its expression was found only in the mammary epithelial cells. Glucocorticoid was essential for LAO gene expression. Thus, the LAO gene is expressed acutely upon the onset of milk synthesis. LAO mRNA increased 1 day before parturition, peaked during early to mid-lactation, and decreased at the end of lactation. This is the first demonstration showing that LAO is present in milk. Mastitis is caused by an intramammary bacterial infection. As mouse milk produced H(2)O(2) using endogenous free amino acids, we suggest that LAO, together with free amino acids, is responsible for killing bacteria in the mammary gland.
authors.affiliation: Department of Animal Breeding, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, Japan.
authors.forename: Youping
authors.initials: Y
authors.lastname: Sun
authors.forename: Eriko
authors.initials: E
authors.lastname: Nonobe
authors.forename: Youko
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kuraishi
authors.forename: Fugaku
authors.initials: F
authors.lastname: Aoki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Senkiti
authors.initials: S
authors.lastname: Sakai
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D004247:DNA; D018076:DNA, Complementary; D004591:Electrophoresis, Polyacrylamide Gel; D050830:L-Amino Acid Oxidase; D051379:Mice; D008892:Milk / Q000201:enzymology*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D004247:DNA; D000594:Amino Acid Oxidoreductases; D050830:L-Amino Acid Oxidase