Biología y Biomedicina >
Centro de Biología Molecular Severo Ochoa (CBM) >
(CBM) Artículos >
Closed Access item Induced biosynthesis of liver glucokinase
|Keywords:||Glucokinase, Messenger RNA, Hexosemonophosphate, Liver|
|Citation:||Advances in Enzyme Regulation, 2: 177-188 (1964)|
|Abstract:||A glucokinase qualitatively and quantitatively adequate as the first and limiting step in the synthesis of glycogen from glucose in liver has recently been identified in normal fed rats. In contrast with hexokinase, that also occurs in liver, glucokinase activity disappears in fasted and alloxandiabetic animals. The high Km, glucose-6-P-insensitive glucokinase, does not occur in muscle, nor in any of several other tissues examined. This and other indirect evidence suggest that the glucokinase is a unique enzyme of the parenchymal cells of the liver, and that the hexokinase measured in liver homogenates is present in the non-parenchymal cells.
Glucokinase reappears in diabetic and fasted animals within a few hours after administration of insulin or refeeding respectively. Glucose administration alone is also effective in provoking the reappearance of glucokinase activity in previously fasted rats. Liver hexokinase remains essentially unaltered in these conditions. Inhibition of the reappearance of glucokinase by ethionine and p-fluorophenylalanine, largely counteracted by methionine and phenylalanine respectively, suggests that actual synthesis of the enzyme is involved. A similar effect of actinomycin supports this conclusion while it further suggests that formation of messenger RNA is involved. These results suggest that liver glucokinase is an inducible enzyme whose synthesis is induced directly or indirectly, by insulin.
The differences in the hexosemonophosphate pathway between liver and muscle, their metabolic regulation, and the relationship with other pathways is discussed.|
|Publisher version (URL):||http://dx.doi.org/10.1016/S0065-2571(64)80012-1|
|Appears in Collections:||(CBM) Artículos|
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.