Catabolic alanine racemase from Salmonella typhimurium: DNA sequence, enzyme purification, and characterization.
The alanine racemase encoded by the Salmonella typhimurium dadB gene was purified to 90% homogeneity from an overproducing strain. At 37 degrees C the enzyme has a specific activity of 1400 units/mg (V max, L- to D-alanine). Active enzyme molecules are monomers of Mr 39 000 with one molecule of pyridoxal 5'-phosphate bound per subunit. The Km's for L- and D-alanine are 8.2 and 2.1 mM, respectively. Measurement of turnover numbers yielded the expected Keq value of 1.0. Determination of 22 of the 25 N-terminal amino acid residues of the purified polypeptide allowed localization of cloned DNA encoding the structural gene. Sequencing of subcloned DNA revealed that the dadB gene encodes a polypeptide of 356 amino acids whose calculated molecular weight (apoenzyme) was 39 044.
D000411:Alanine Racemase / Q000235:genetics* / Q000302:isolation & purification; D000591:Amino Acid Isomerases / Q000235:genetics*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001483:Base Sequence; D004269:DNA, Bacterial / Q000032:analysis*; D007700:Kinetics; D008970:Molecular Weight; D012486:Salmonella typhimurium / Q000201:enzymology* / Q000235:genetics
D000596:Amino Acids; D004269:DNA, Bacterial; D000591:Amino Acid Isomerases; D000411:Alanine Racemase