Purification and characterization of a cold-adapted isocitrate lyase and expression analysis of the cold-inducible isocitrate lyase gene from the psychrophilic bacterium Colwellia psychrerythraea.
Isocitrate lyase (ICL) from Colwellia psychrerythraea, a psychrophilic bacterium, was purified and characterized. The subunit molecular mass was 64 kDa, which is larger than that of other bacterial ICLs. The optimal temperature for its activity was 25 degrees C, the value of K(m) for the substrate ( DL-isocitrate) was minimum at 15 degrees C, and the catalytic efficiency ( k(cat)/ K(m)) value was maximum at 20 degrees C. Furthermore, the enzyme was remarkably thermolabile and completely inactivated by incubation for 2 min at 30 degrees C. These features indicate that ICL from this bacterium is a typical cold-adapted enzyme. A partial amino acid sequence of the C. psychrerythraea ICL was very similar to that of the closely related psychrophile Colwellia maris. Expression of the gene encoding the C. psychrerythraea ICL was found to be induced by low temperatures and by acetate in the medium. The cold adaptation of the catalytic properties of ICL and the stimulated expression of its gene at low temperatures strongly suggest that this enzyme is important for the growth of this bacterium in a cold environment.
Watanabe
Seiya
S
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Kita 10-jo Nishi 8-chome, Kita-ku, Sapporo 060-0810, Japan.
Yamaoka
Naoto
N
Fukunaga
Noriyuki
N
Takada
Yasuhiro
Y
D000222:Adaptation, Physiological; D034241:Alteromonadaceae / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D002413:Cations, Divalent / Q000494:pharmacology; D003080:Cold Temperature; D004790:Enzyme Induction; D015964:Gene Expression Regulation, Bacterial; D007522:Isocitrate Lyase / Q000096:biosynthesis / Q000235:genetics*; D007700:Kinetics; D008969:Molecular Sequence Data; D011489:Protein Denaturation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013816:Thermodynamics
D001426:Bacterial Proteins; D002413:Cations, Divalent; D007522:Isocitrate Lyase