Pentose metabolism and pentosuria

Abstract

The metabolism of pentoses is reviewed. The pentose phosphate pathway (6-phosphogluconate oxidation pathway) is the source of tissue d-ribose and perhaps d-2-deoxyribose as well. In certain tissues it also contributes to the net oxidation of glucose and probably supplies reduced triphosphopyridine nucleotide for biosynthetic reactions. Little is known about the importance of the glucuronate-xylulose cycle, except that from it the l-ascorbic acid produced by the rat is derived. It is significant that l-xylulose, the characteristic urinary sugar of essential pentosuria, is an intermediate in this pathway. It can be stated with considerable certainty that essential pentosuria is a harmless biochemical anomaly linked to a rare recessive gene which is virtually restricted to individuals of Jewish origin. The exact nature of the defect has not been clearly determined. The questionable existence of other types of pentosuria is discussed.