STUDIES OF PENTOSE METABOLISM IN NORMAL SUBJECTS AND IN PATIENTS WITH PENTOSURIA AND PENTOSURIA TRAIT*

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Abstract
Endogenous serum l-xylulose concentration exceeds 1 mg. per 100 ml. in pontosuric patients, and the level rises several-fold following administration of glucuronolaetone. L-xylulose is not detectable in the serum of most nonpentosuric subjects before administration of glucuronolactone, but appears following ingestion of this compound. The increase in both serum and urine pentose levels after glucuronolactone is greater in patients with pentosuria trait than in control subjects. A comparison of serum and urine levels suggests that both pentosuric and nonpentosuric subjects excrete most of the l-xylulose which is presented to the renal tubules. TPN-xylitol (l-xylulose) dehydrogenase, the enzyme believed to be defective in subjects with pentosuria, can be demonstrated in normal human liver and in rat and guinea-pig liver and kidney.