A Reassessment of the Phospholipid Dependence of Membrane-Bound Enzymes, with Special Reference to GIucose-6-Phosphatase and Na+, K+-Dependent Adenosine Triphosphatase

Abstract

It is suggested that the specific involvement of phospholipid in either the expression or constraint of glucose-6-phosphatase activity is not conclusively established by the existing experimental evidence. The physiological significance of an apparent requirement for phosphatidylserine for Na+, K+-dependent adenosine triphosphatase activity is also questioned. The need for a critical reassessment of past conclusions in the light of present knowledge is emphasized.

The Effects of Fasting on Glucose-6-Phosphatase of Mouse Liver and Kidney

“…This increase was not apparent when the enzyme was assayed in the absence of detergent. Our finding supports the concept that deoxycholate potentiates the fasting response (3,7). This is more evident after 48 h fasting, where the liver enzyme levels are approximately 1.5-fold of control values when assayed in the absence of deoxycholate but increases up to 1.8-fold when assayed in its presence.…”

Phospholipid content and activity of pure uridine diphosphate-glucuronyltransferase from rat liver

“…Exposure of pure UDP-glucuronyltransferase to similar treatment with phospholipase C did not cause any measurable enzyme inhibition, presumably because of the virtual absence of phospholipid bound to the pure transferase. Duck-Chong (1976) suggested that membrane-bound enzyme activities may be supported by the presence of detergents acting as lipid substitutes. Furthermore, Lu et al (1974) showed that the benzphetamine (N-benzyl-N'dimethylphenethylamine) N-demethylase activity of a reconstituted microsomal enzyme system was stimulated when a number of detergents were substituted for a crude liver lipid fraction in the reconstituted system: some detergents were as effective as lipid in eliciting enzyme activity.…”