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 degrees 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 degrees 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 degrees C.