期刊
FEBS JOURNAL
卷 273, 期 12, 页码 2722-2729出版社
BLACKWELL PUBLISHING
DOI: 10.1111/j.1742-4658.2006.05290.x
关键词
archaea; hyperthermophile; Pyrococcus furiosus; thermostability; threonine dehydrogenase
The gene encoding a threonine dehydrogenase (TDH) has been identified in the hyperthermophilic archaeon Pyrococcus furiosus. The Pf-TDH protein has been functionally produced in Escherichia coli and purified to homogeneity. The enzyme has a tetrameric conformation with a molecular mass of approximate to 155 kDa. The catalytic activity of the enzyme increases up to 100 degrees C, and a half-life of 11 min at this temperature indicates its thermostability. The enzyme is specific for NAD(H), and maximal specific activities were detected with L-threonine (10.3 U.mg(-1)) and acetoin (3.9 U.mg(-1)) in the oxidative and reductive reactions, respectively. Pf-TDH also utilizes L-serine and D-threonine as substrate, but could not oxidize other L-amino acids. The enzyme requires bivalent cations such as Zn2+ and Co2+ for activity and contains at least one zinc atom per subunit. K-m values for L-threonine and NAD(+) at 70 degrees C were 1.5 mM and 0.055 mM, respectively.
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