ABSTRACT
Induction studies on Aerobacter aerogenes strain PRL-R3, using ribitol as the inducer-substrate, indicated that two enzymes of ribitol catabolism, ribitol dehydrogenase and d-ribulokinase, are coordinately induced. The utilization of d-arabinose as a substrate resulted in the induction of ribitol dehydrogenase as well as d-ribulokinase. Mutants which were constitutive for ribitol dehydrogenase were also constitutive for d-ribulokinase. In contrast, d-xylulokinase and d-arabitol dehydrogenase did not appear to be coordinately controlled. Induction studies and examination of d-arabitol dehydrogenase constitutive mutants indicated that the three enzymes of the converging pathways for d-arabitol and d-xylose catabolism are under separate control.
Subject(s)
Alcohol Oxidoreductases/metabolism , Alcohols/metabolism , Enterobacter/metabolism , Molecular Biology , Phosphotransferases/metabolism , Enterobacter/enzymology , Enzyme Induction , Enzyme Repression , Mutation , Xylose/metabolismABSTRACT
The incubation of Aerobacter aerogenes PRL-R3 with ribitol resulted in the induction of ribitol dehydrogenase and d-ribulokinase, coordinately controlled enzymes of the pathway of ribitol catabolism. A dehydrogenase-negative mutant was unable to induce d-ribulokinase activity following incubation with ribitol. Similar experiments using a kinase-negative mutant resulted in normal induction of ribitol dehydrogenase, as compared to the wild-type PRL-R3 strain. Constitutive or induced cells for l-fucose isomerase were capable of catalyzing the isomerization of d-arabinose to d-ribulose. In contrast to the experiments using ribitol as the substrate, the isomerization of d-arabinose resulted in the induction of d-ribulokinase with dehydrogenase-negative cells. These data indicated that d-ribulose, rather than ribitol, acts as the inducer of the enzymes for ribitol degradation.
