although the enzyme udp-glucose dehydrogenase from beef liver ( e.c . 1.1.1.22 ) is known to abstract the pro-r hydrogen stereospecifically at carbon 6 of the glucose moiety of the substrate by a reversible step in converting udp-glucose to udp-alpha-d-gluco-hexodialdose ( udp-glc-6-cho ) , prolonged incubation of the enzyme with udp-glucose and tritium-labeled nadh , under conditions favoring hydrogen exchange between the two , results in equivalent labeling of both hydrogens at carbon 6 .
C0041119
tritium
C0020275
hydrogens