Novel Psychrophilic and Thermolabile l -Threonine Dehydrogenase from Psychrophilic Cytophaga sp. Strain KUC-1

• DOI: 10.1128/jb.185.15.4483-4489.2003
• Publication Date: 2003-07-16T22:06:22Z
• Authors: Takayuki Kazuoka; Shouhei Takigawa; Noriaki Arakawa; Yoshiyuki Hizukuri; Ikuo Muraoka; Tadao Oikawa; Kenji Soda
• Keywords: Psychrophile; Thermolabile; Strain (injury); Eubacterium

A psychrophilic bacterium, Cytophaga sp. strain KUC-1, that abundantly produces a NAD(+)-dependent L-threonine dehydrogenase was isolated from Antarctic seawater, and the enzyme purified. The molecular weight of estimated to be 139,000, subunit determined 35,000. is homotetramer. Atomic absorption analysis showed contains no metals. In these respects, distinct other dehydrogenases have thus far been studied. L-Threonine DL-threo-3-hydroxynorvaline were substrates, NAD(+) some its analogs served as coenzymes. maximum activity at pH 9.5 45 degrees C. kinetic parameters are highly influenced by temperatures. K(m) for lowest 20 Dead-end inhibition studies with pyruvate adenosine-5'-diphosphoribose reaction proceeds via ordered Bi mechanism in which binds an prior 2-amino-3-oxobutyrate released NADH. gene cloned into Escherichia coli, nucleotides sequenced. open reading frame 939 bp encoding protein 312 amino acid residues. sequence significant similarity UDP-glucose 4-epimerase Staphylococcus aureus belongs short-chain dehydrogenase-reductase superfamily. contrast, E. coli medium-chain alcohol family, not all similar enzyme. significantly epimerase, shown first time. residues playing important role catalysis human 4-epimerases conserved enzyme, except participating substrate binding.