Pathway of galactitol catabolism in Klebsiella pneumoniae.

Cell extracts of galactitol-grown Klebsiella pneumoniae phosphorylate galactitol by means of a phosphoenolpyruvate:galactitol phosphotransferase system. Both the product and authentic L-galactitol-l-P are oxidized with NAD⁺ by a dehydrogenase to yield D-tagatose-6-P, which is phosphorylated with ATP by a kinase to form D-tagatose-1,6-P₂. This ketohexose diphosphate is cleaved by an aldolase to yield dihydroxyacetone-P and D-glyceraldehyde-3-P. Mutants deficient in either the dehydrogenase, kinase, or aldolase failed to grow on galactitol, indicating that the described pathway is of physiological significance in this organism.