A Thermolabile Triosephosphate Isomerase from the Psychrophile Vibrio sp. Strain ANT-300

We report the isolation of a gene encoding triosephosphate isomerase (TIM; EC 5.3.1.1) from Vibrio sp. strain ANT-300, a psychrophilic marine eubacterium that grows optimally at 7°C. The deduced primary sequence of this isomerase is 50% identical to Escherichia coli TIM and 37% identical to the isomerase of the psychrotroph Moraxella sp. TA137. Transformation with this gene allowed growth of a TIM-deficient E. coli strain on selective media, but only at temperatures below 30°C. The temperature dependence of this complementation is likely to result from an intrinsic thermolability of the isomerase. Indeed, the TIM activity present in ANT-300 lysates is markedly heat-sensitive, with a half-life of inactivation of 520 s at 25°C.