AJP - Gastrointestinal and Liver Physiology, Vol 256, Issue 1 67-G71, Copyright © 1989 by American Physiological Society
Reduction of 7-ketolithocholic acid by human liver enzyme preparations in vitro
Y. Amuro, W. Yamade, K. Kudo, T. Yamamoto, T. Hada and K. Higashino
Third Department of Internal Medicine, Hyogo College of Medicine, Japan.
The formation of chenodeoxycholic and ursodeoxycholic acids from
7-ketolithocholic acid by human liver preparations was examined in vitro.
Liver preparations were incubated with 7-ketolithocholic acid at pH 5.5 in
a sodium-potassium-phosphate buffer containing NADPH or NADH. The products
formed were analyzed by gas chromatography and gas chromatography-mass
spectrometry. Results showed that chenodeoxycholic and ursodeoxycholic
acids could be formed from 7-ketolithocholic acid by human liver enzyme(s).
The enzyme(s) required NADPH but not NADH as coenzyme and was localized
largely in the microsomes. The conjugated 7-ketolithocholic acid,
especially the taurine conjugated, was predominantly reduced to
chenodeoxycholic acid, whereas the unconjugated 7-ketolithocholic acid was
not reduced well to either chenodeoxycholic acid or ursodeoxycholic acid.
Thus the reduction of 7-ketolithocholic acid by human liver enzyme(s) was
found to be dependent on whether the substrate was conjugated or not.
