CHARACTERIZATION OF MALATE-DEHYDROGENASE FROM DEEP-SEA PSYCHROPHILIC VIBRIO SP STRAIN NO-5710 AND CLONING OF ITS GENE

A metabolic key enzyme malate dehydrogenase (MDH) was purified from a deep-sea psychrophilic bacterium, Vibrio sp. strain no. 5710. The enzy me displayed an optimal activity shifted toward lower temperature and a pronounced heat lability. A gene encoding this enzyme was isolated a nd cloned. Recombinant Escherichia coli cells harboring the isolated c lone expressed MDH activity with temperature stability identical to th at of the parental psychrophile. Nucleotide sequencing of the gene rev ealed that its primary sequence was similar to that of a mesophile E. coli MDH (78% amino acid identity), for which the three-dimensional st ructure is known. The enzyme is thus suitable for the analysis of mole cular adaptations to low temperatures.