title: Molecular characterization of alanine racemase in the Kuruma prawn Marsupenaeus japonicus.
abstract: Aquatic crustaceans and some bivalve mollusks are known to contain copious amounts of free d-alanine in their tissues. For the first time in the animal kingdom, we have isolated a cDNA clone encoding alanine racemase from the muscle and hepatopancreas of the kuruma prawn Marsupenaeus japonicus. The recombinant enzyme expressed in Escherichia coli exhibited alanine recemase activity. The deduced amino-acid sequence showed only 23-31% identity to bacterial alanine racemases. However, the active site residues and some residues that interact with pyridoxal 5'-phosphate were also conserved in M. japonicus enzyme. There was higher alanine racemase mRNA expression in hepatopancreas than in muscle. In contrast, the d-alanine content in hepatopancreas was lower than that in muscle, suggesting that the physiological functions of free d-alanine may differ among tissues. These data suggest that the alanine racemase gene has been conserved from bacteria to invertebrates throughout a long evolutionary time scale.
authors.affiliation: Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Yoshikawa
authors.forename: Shigeru
authors.initials: S
authors.lastname: Okada
authors.forename: Hiroki
authors.initials: H
authors.lastname: Abe
mesh_terms: D000411:Alanine Racemase / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D033561:Penaeidae / Q000201:enzymology* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D011994:Recombinant Proteins; D000411:Alanine Racemase