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B6db references: 10080917

type Journal Article
authors Okubo, Y.; Yokoigawa, K.; Esaki, N.; Soda, K.; Kawai, H.
title Characterization of psychrophilic alanine racemase from Bacillus psychrosaccharolyticus
journal Biochem Biophys Res Commun
sel selected
ui 10080917
year (1999)
volume 256
number 2
pages 333-40
keywords Alanine Racemase/biosynthesis/chemistry/isolation & purification/*metabolism
abstract A psychrophilic alanine racemase gene from Bacillus psychrosaccharolyticus was cloned and expressed in Escherichia coli SOLR with a plasmid pYOK3. The gene starting with the unusual initiation codon GTG showed higher preference for codons ending in A or T. The enzyme purified to homogeneity showed the high catalytic activity even at 0 degrees C and was extremely labile over 35 degrees C. The enzyme was found to have a markedly large Km value (5.0 microM) for the pyridoxal 5'-phosphate (PLP) cofactor in comparison with other reported alanine racemases, and was stabilized up to 50 degrees C in the presence of excess amounts of PLP. The low affinity of the enzyme for PLP may be related to the thermolability, and may be related to the high catalytic activity, initiated by the transaldimination reaction, at low temperature. The enzyme has a distinguishing hydrophilic region around the residue no. 150 in the deduced amino acid sequence (383 residues), whereas the corresponding regions of other Bacillus alanine racemases are hydrophobic. The position of the region in the three dimensional structure of C atoms of the enzyme was predicted to be in a surface loop surrounding the active site. The region may interact with solvent and reduce the compactness of the active site.
last changed 2009/01/09 13:22

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