1 Department of Biochemistry, School of Medicine, University of Southern California, Los Angeles, California 90027
2 Department of Pediatrics, School of Medicine, University of Southern California, Los Angeles, California 90027
3 Childrens Hospital of Los Angeles, Los Angeles, California 90027
4 Los Angeles County General Hospital, Los Angeles, California 90027
Kabacy, et al. have shown by the uridine diphosphate glucose (UDPG) consumption assay that galactose-1-phosphate uridyl transferase (transferase) activity in hemolysates of newborn infants is significantly lower than for normal adults. Recent studies of hemolysate UDPGalactose-4-epimerase (epimerase) in newborns have suggested the possibility that the results of Kabacy, et al. may have been influenced by regeneration of UDPG by the epimerase reaction. A necessary condition for assay of transferase by UDPG consumption is that epimerase activity be negligible. We now have shown that epimerase activity in hemolysates from newborn infants is markedly elevated and, in contrast to findings with normal adults, substantial epimerase activity is present in the absence of exogenous oxidized nicotinamide adenine dinucleotide (NAD).