Enzymatic characterization and comparison of three sugar dehydrogenases from a pseudomonad.

The regulation of a number of sugar dehydrogenases in a pseudomonad has been described previously as being loosely coordinated (1). Most enzymes of bacteria which are regulated in concert have been found to function as parts of a common metabolic pathway, such as those involved in the biosynthesis of histidine and arginine (2, 3), or those involved in galactose and lactose metabolism (4, 5). The sugar dehydrogenases of Pseudomonas, however, are the initial enzymes in separate metabolic pathways for the respective sugars (6-8), and their coordinate regulation may be the result of a mechanism quite different from the popular genetic model proposed by Jacob and Monod (5). In view of the catalytic similarities and regulatory relationships among these enzymes, a close examination of their enzymatic and physical properties might reveal further interesting relationships. Three of the dehydrogenases described have been purified to a degree approaching homogeneity (Q), and their comparative enzymatic properties are reported here. Their physical properties are reported elsewhere (10).