A NOVEL UDP-SUGAR, UDP-3-KETOGLUCOSAMINE OR UDP-4-KETOGLUCOSAMINE, FROM BOVINE HEART-MUSCLE REDUCES METMYOGLOBIN WITH NAD(P)H

3-Ketoglucose and similar ketosugars have been identified in microorga nisms only and little is known about their functions. UDP-sugars are w idely found as an intermediate in sugar metabolism in living organisms , Yet what role UDP-sugars play, or whether they play a direct role in metabolism, is still unknown. UDP-sugars were isolated and purified f rom bovine heart muscle, and a UDP-sugar fraction capable of NAD(P)H-d ependent catalytic reduction of metmyoglobin was detected. Subsequent identification revealed that the active UDP-sugar was UDP-3- or UDP-4- ketoglucosamine. These compounds were purified from bovine cardiac mus cle by ultrafiltration, anion-exchange column chromatography and rever se-phase chromatography. They were further characterized by determinat ion of their chemical reducing activity, bycomparison with synthetic U DP-3- or UDP-4-ketoglucosamine standards using high-performance liquid chromatography, by estimation of molecular mass using fast atom bomba rdment mass spectrometry, and by Fourier transform infrared microspect roscopy and electron probe microanalysis. The results suggest that UDP -3- or UDP-4-ketoglucosamine reduces metmyoglobin in bovine cardiac mu scle. It is important that the reducing activity displayed by this ket osugar is not the effect of UDP-3- or UDP-4-ketoglucosamine alone but depends on NAD(P)H. In other words, this action of UDP-3- or UDP-4-ket oglucosamine is catalytic.