A reassessment of the phospholipid dependence of membrane-bound enzymes, with special reference to glucose-6-phosphatase and Na+, K+-dependent adenosine triphosphatase.

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.