Identification, purification, and characterization of a D-arabinitol-specific dehydrogenase from Candida tropicalis.

A novel D-arabinitol (DA) dehydrogenase was identified and purified more than 300-fold from Candida tropicalis. The enzyme is specific for DA and catalyzes the NAD(+)-dependent oxidation at carbon 4 to yield D-ribulose. Purification was accomplished by a combination of protamine sulfate and ammonium sulfate precipitation and dye ligand chromatography on a reactive yellow 86 column. The apparent Km of the enzyme for DA ([NAD+] = 2.2 mM) is 39.8 mM. The apparent Km for NAD+ ([DA] = 384 mM) is 0.12 mM. The pH-optimum for the enzymatic oxidation of DA is approximately 10. Cofactor stereospecificity studies demonstrate that the enzyme catalyzes transfer of the 4(S) hydrogen of NADH with D-ribulose as substrate. The polyol substrate specificity of the present DA dehydrogenase makes the enzyme potentially useful for the development of a simple and specific method for the measurement of DA, a metabolite of pathogenic Candida spp. which has been described as a marker for disseminated candidiasis.