PARALLEL INDUCTION OF d -ARABITOL AND d -SORBITOL DEHYDROGENASES

Abstract

Two inducible diphosphopyridine nucleo-tide-linked dehydrogenases are described in a bacterium isolated from the soil Cellvibrio polyoltrophicus ATCC 14774. The first enzyme catalyzes the dehydrogenation of D-arabitol to D-xylulose and D-mannitol to D-fructose. The data suggest that in vivo this enzyme has the dual function of the utilization of both of these polyhydric alcohols. The second enzyme was found to act only on D-sorbitol, converting it to D-fructose. Evidence for its physiological function as a D-sorbitol dehydrogenase is also given. Both of these enzymes were found to be induced in parallel by any of the three polyhydric alcohols, D-arabitol, D-mannitol and D-sorbitol. A common stereoconfiguration of the inducers for these enzymes is suggested. The parallel evolution of substrate specificity and inducer specificity is discussed with respect to the functional advantage that such a selective process might offer,.