Flip‐Flop Mechanisms in Enzymology

Abstract

A new mechanism is proposed which permits a clear‐cut interpretation of the properties and features characteristic of the alkaline phosphatase of Escherichia coli. It is called the Flip‐Flop mechanism. The Flip‐Flop mechanism implies alternating functions for each of the two active sites of the phosphatase. The phosphorylation of one site is concurrent with the dephosphorylation of the other site. The alkaline phosphatase is considered to be a model. The functional and evolutive advantages of the Flip‐Flop mechanism suggest that it might be fairly common among polymeric enzymes with Michaelian kinetics. Data already reported in the literature for other enzymes are discussed in light of the Flip‐Flop mechanism.