Studies on the interactions between phospholipids and membrane-bound enzymes in microsomes. Effects of phospholipases C on kinetic properties of the glucose-6-phosphatase system in rat liver microsomes

J Biochem. 1983 Feb;93(2):537-46. doi: 10.1093/oxfordjournals.jbchem.a134208.

Abstract

Through kinetic analysis, the relationships between the glucose-6-phosphatase system and constituent phospholipids were studied in rat liver microsomes. When phosphoglycerides such as phosphatidylcholine and phosphatidylethanolamine on the microsomal membrane were hydrolyzed by phospholipase C of C. perfringens, the activities of glucose-6-P phosphohydrolase and glucose-6-P:glucose phosphotransferase both decreased with or without subsequent exposure to taurocholate. In these cases, the Michaelis constants (Km) for glucose-6-P were increased, concomitant with the decrease in the maximal velocities (Vmax) for glucose-6-P hydrolysis. On exposure to taurocholate, the apparent Km for glucose of phosphotransferase was decreased. When phosphatidylinositol was hydrolyzed by phosphatidylinositol-specific phospholipase C of B. thuringiensis, the activities of phosphohydrolase and phosphotransferase were both decreased on exposure to taurocholate. In this case, the value of Vmax of phosphohydrolase was decreased and that of Km for glucose-6-P was slightly decreased, while the apparent Km for glucose of phosphotransferase was increased. Without exposure to detergent, the activities of phosphohydrolase and phosphotransferase both decreased at glucose-6-P concentrations higher than 10 mM. However, at a concentration lower than 1 mM, the activity of phosphohydrolase became higher than that of the control, and Vmax and Km for glucose-6-P were decreased. A similar tendency was also observed in microsomes where membranous phosphatidylinositol was hydrolyzed, when they were treated with DIDS (an anion-transport inhibitor). From these results, it is concluded that the activity of glucose-6-phosphatase is greatly influenced by changes of the phospholipids on the microsomal membrane, and the activity of glucose-6-P translocase is stimulated by the breakdown of phosphatidylinositol.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antiporters
  • Clostridium perfringens / enzymology
  • Glucose-6-Phosphatase / metabolism*
  • Intracellular Membranes / physiology
  • Kinetics
  • Male
  • Membrane Lipids / physiology*
  • Microsomes, Liver / enzymology*
  • Monosaccharide Transport Proteins
  • Phosphatidylinositols
  • Phospholipases / pharmacology*
  • Phospholipids / physiology*
  • Phosphotransferases / metabolism
  • Rats
  • Rats, Inbred Strains
  • Substrate Specificity
  • Type C Phospholipases / metabolism
  • Type C Phospholipases / pharmacology*

Substances

  • Antiporters
  • Membrane Lipids
  • Monosaccharide Transport Proteins
  • Phosphatidylinositols
  • Phospholipids
  • Slc37a4 protein, rat
  • glucose 6-phosphate(transporter)
  • Phosphotransferases
  • Phospholipases
  • Glucose-6-Phosphatase
  • Type C Phospholipases