AN AUTOMATED ENZYMATIC METHOD FOR MEASUREMENT OF D-ARABINITOL, A METABOLITE OF PATHOGENIC CANDIDA SPECIES

An automated enzymatic method wa developed for the measurement Of D-ar abinitol in human serum. The assay is based on a novel, highly specifi c D-arabinitol dehydrogenase from Candida tropicalis. This enzyme cata lyzes the oxidation of D-arabinitol to D-ribulose and the concomitant reduction of NAD+ to NADH. The NADH produced is used in a second react ion to reduce p-iodonitrotetrazolium violet (INT) to INT-formazan, whi ch is measured spectrophotometrically. The entire reaction sequence ca n be performed automatically on a COBAS MIRA-S clinical chemistry anal yzer (Roche Diagnostic Systems, Inc., Montclair, N.J.). Replicate anal yses of human sera supplemented With D-arabinitol over a concentration range of 0 to 40 muM demonstrated that the pentitol could be measured with an accuracy of +/-7% and a precision (standard deviation) of +/- 0.4 muM. SeruM D-arabinitol measurements correlated with those determi ned by gas chromatography (r = 0.94). The enzymatic method is unaffect ed by L-arabinitol, D-mannitol, or other polyols commonly found in hum an serum. Any of 17 therapeutic drugs potentially present in serum did not significantly influence assay performance. Data illustrating the application of the assay in patients for possible diagnosis of invasiv e candidiasis and the monitoring of therapeutic intervention are prese nted. The automated assay described here was developed to facilitate t he investigation of D-arabinitol as a serum marker for invasive Candid a infections.