Purification and properties of a histidine decarboxylase from Tetragenococcus muriaticus, a halophilic lactic acid bacterium.
OBJECTIVE
A histidine decarboxylase from Tetragenococcus muriaticus, a halophilic histamine-producing bacterium isolated from Japanese fermented squid liver sauce, was purified to homogeneity, for the first time.


RESULTS
The enzyme was purified 16-fold from cell-free extract by ammonium sulphate precipitation, anion exchange chromatography and hydroxyapatite chromatography. The pure enzyme consisted of two polypeptide chains with molecular mass of 28.8 and 13.4 kDa. The N-terminal amino acid sequences of these polypeptides highly correlated with those of the alpha- and beta-chains of other Gram-positive bacterial histidine decarboxylases. The optimum and stable pH for the enzyme was 4.5-7.0 and 4.0-7.0, respectively. This enzyme did not decarboxylate lysine, arginine, tyrosine, tryptophan and ornithine. The enzyme activity decreased with the addition of NaCl. At pH 4.8, the Vmax and Km values were 16.8 micromol histamine min-1 mg-1 and 0.74 mmol l-1, respectively.


CONCLUSIONS
The very similar physiological properties of this enzyme and almost identical N-terminal amino acid sequences to those from other Gram-positive bacteria indicated that this enzyme may be evolutionally highly conserved among Gram-positive bacteria.


CONCLUSIONS
Information on this enzyme could be useful for studying the mechanism of histamine accumulation in salted foods. In addition, the N-terminal amino acid sequence can be utilized to design oligonucleotide probes, which may prove valuable in the rapid monitoring of halophilic histamine producers in salted products.
Konagaya
Y
Y
Department of Food Science and Technology, Tokyo University of Fisheries, Minato-ku, Tokyo, Japan.
Kimura
B
B
Ishida
M
M
Fujii
T
T
D000595:Amino Acid Sequence; D004789:Enzyme Activation / Q000502:physiology; D005516:Food Microbiology; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D006632:Histamine / Q000378:metabolism; D006640:Histidine Decarboxylase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007777:Lactobacillaceae / Q000201:enzymology*; D008969:Molecular Sequence Data; D012492:Salts / Q000378:metabolism
D012492:Salts; D006632:Histamine; D006640:Histidine Decarboxylase