Kinetics of ethanol inhibition of galactose elimination in perfused pig liver
- 1 January 1977
- journal article
- research article
- Published by Taylor & Francis in Scandinavian Journal of Clinical and Laboratory Investigation
- Vol. 37 (6), 487-494
- https://doi.org/10.3109/00365517709101836
Abstract
The effect of ethanol (5–25 mM) on the galactose elimination kinetics in the intact liver was studied in the isolated perfused pig liver, using the steady-state infusion technique. Ethanol reduced galactose-Vmax, on average to 0·07 mmol/min kg liver in six experiments from 0·43 mmol/min kg obtained in control experiments without ethanol. Also Km was significantly reduced from 0·23 mmol/l plasma water to 0·03 mmol/l. Ethanol increased UDP-galactose ten-fold simultaneous with a rise in hepatic outflow ratio of lactate to pyruvate to about 300 from 10; this indicates that ethanol inhibits epimerase. In experiments with increasing galactose elimination rates, the concentration of galactose-1-P increased much less than the concentration of galactose, and the phosphorylation of galactose therefore seems to be rate-limiting. In vitro galactokinase is inhibited by galactose-1-P. In the present study ethanol increased galactose-1-P five to ten times, and the reduction of Vmax and Km by ethanol could be explained by uncompetitive inhibition by galactose-1-P with K1, about 0·1 mmol/l. Ethanol decreased UDP-glucose to about 40% and UTP to less than 5%, probably due to trapping as UDP-galactose. This may depress the forward transferase reaction, and therefore the other co-substrate galactose-1-P rises—and inhibits galactokinase.Keywords
This publication has 15 references indexed in Scilit:
- Orotate decreases the inhibitory effect of ethanol on galactose elimination in the perfused rat liverBiochemical Journal, 1976
- Enzymatic elimination of substrates flowing through the intact liverJournal of Theoretical Biology, 1976
- Galactose Elimination Capacity in the RatScandinavian Journal of Clinical and Laboratory Investigation, 1973
- Liver galactose-l-phosphate uridyl transferase: activity in normal and galactosemic subjectsJCI Insight, 1971
- Trapping of uridine phosphates by D‐galactose in ethanol‐treated liverFEBS Letters, 1970
- Some characteristics and developmental aspects of rat uridine diphosphogalactose 4-epimeraseBiochimica et Biophysica Acta (BBA) - Enzymology, 1969
- Purification and properties of galactokinase from pig liverBiochemical Journal, 1966
- Equilibrium constant of phosphoryl transfer from adenosine triphosphate to galactose in the presence of galactokinaseBiochemical Journal, 1961
- Uridyl Transferases and the Formation of Uridine Triphosphate : Uridyl Transferases and the Formation of Uridine DiphosphogalactoseNature, 1953
- The enzymatic transformation of uridine diphosphate glucose into a galactose derivativeArchives of Biochemistry and Biophysics, 1951