3646-68-2Relevant articles and documents
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Ohdan,S. et al.
, p. 981 - 985 (1973)
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Wolfrom,Cron
, p. 1715 (1952)
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Characterization of d-amino acid aminotransferase from Lactobacillus salivarius
Kobayashi, Jyumpei,Shimizu, Yasuhiro,Mutaguchi, Yuta,Doi, Katsumi,Ohshima, Toshihisa
, p. 15 - 22 (2013/10/22)
We searched a UniProt database of lactic acid bacteria in an effort to identify d-amino acid metabolizing enzymes other than alanine racemase. We found a d-amino acid aminotransferase (d-AAT) homologous gene (UniProt ID: Q1WRM6) in the genome of Lactobacillus salivarius. The gene was then expressed in Escherichia coli, and its product exhibited transaminase activity between d-alanine and α-ketoglutarate. This is the first characterization of a d-AAT from a lactic acid bacterium. L. salivarius d-AAT is a homodimer that uses pyridoxal-5′-phosphate (PLP) as a cofactor; it contains 0.91 molecules of PLP per subunit. Maximum activity was seen at a temperature of 60 °C and a pH of 6.0. However, the enzyme lost no activity when incubated for 30 min at 30 °C and pH 5.5 to 9.5, and retained half its activity when incubated at pH 4.5 or 11.0 under the same conditions. Double reciprocal plots of the initial velocity and d-alanine concentrations in the presence of several fixed concentrations of α-ketoglutarate gave a series of parallel lines, which is consistent with a Ping-Pong mechanism. The Km values for d-alanine and α-ketoglutarate were 1.05 and 3.78 mM, respectively. With this enzyme, d-allo-isoleucine exhibited greater relative activity than d-alanine as the amino donor, while α-ketobutylate, glyoxylate and indole-3-pyruvate were all more preferable amino acceptors than α-ketoglutarate. The substrate specificity of L. salivarius d-AAT thus differs greatly from those of the other d-AATs so far reported.
Reactivities of some aldoses and aldosamines towards potassium bromate in hydrochloric acid medium
Sen Gupta, Kalyan Kali,Debnath, Nandadulal,Bhattacharjee, Nandini,Banerjee, Amalendu,Basu, Samarendra Nath
, p. 152 - 156 (2007/10/03)
The kinetics of oxidation of some aldoses and aminosugars by potassium bromate in hydrochloric acid medium have been studied. The reactions appear to proceed through the intermediate formation of bromate esters followed by the decomposition of the esters to give products. Hydrogen-ion accelerates tide rate of each reaction. The thermodynamic values associated with the equilibrium stage and the activation parameters associated with the rate- determining step have been computed.