Changing activities of galactose-metabolizing enzymes during perfusion of suckling-rat liver.
The specific activities of the galactose-metabolizing enzymes, galactokinase (EC 2.7.1.6), galactose-1-phosphate uridyltransferase (EC 2.7.7.12), and UDPgalactose 4-epimerase (EC 5.1.3.2), in suckling-rat livers perfused for 90 min with 1 and 4 mM galactose fluctuate significantly with a different pattern of change for each enzyme. Perfusion for 30 min with galactose resulted in a significant increase of transferase specific activity followed by a precipitous decline to about one-fifth of the activity in unperfused liver at 90 min. The increase in transferase activity was also observed when D-glucose was perfused but not when L-glucose, D-fructose, D-xylose, or D-ribose was added to the perfusate. No such changes in transferase activity were observed when adult-rat liver was perfused with galactose. Epimerase activity in the suckling-rat liver was relatively low, and the changes in its activity correlated best with the uptake rate of galactose. The perfused suckling-rat liver may provide a model system for examination of factors that modulate the specific activity of galactose-metabolizing enzymes and effect the metabolism of galactose.
D000818:Animals; D000833:Animals, Suckling; D002238:Carbohydrate Epimerases / Q000378:metabolism*; D005260:Female; D005686:Galactokinase / Q000378:metabolism*; D005690:Galactose / Q000008:administration & dosage / Q000378:metabolism*; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D009713:Nucleotidyltransferases / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D013997:Time Factors; D014534:UDPglucose 4-Epimerase / Q000378:metabolism*; D005694:UTP-Hexose-1-Phosphate Uridylyltransferase / Q000378:metabolism*
D005686:Galactokinase; D009713:Nucleotidyltransferases; D005694:UTP-Hexose-1-Phosphate Uridylyltransferase; D002238:Carbohydrate Epimerases; D014534:UDPglucose 4-Epimerase; D005690:Galactose