Mechanistic origin of the kinetic cooperativity of hexokinase type L1 from wheat germ.

A theoretical analysis is presented which shows that initial velocity data for hexokinase L1 catalysis of glucose phosphorylation by MgATP cannot be reconciled with the observed rate of the 'mnemonical' conformational transition which has been proposed to account for the kinetic cooperativity of the enzyme. The basic kinetic properties of hexokinase L1 and other allegedly 'mnemonical' enzymes appear to be fully consistent with an ordered ternary-complex mechanism in which the leading substrate participates in abortive-complex formation. It is concluded that, so far, no enzyme displaying kinetic cooperativity has been convincingly demonstrated to operate by a 'mnemonical' type of reaction mechanism.