The stereochemical course of phosphoryl transfer catalysed by glucokinase

Adenosine 5'-[gamma(S)-16O,17O,18O]triphosphate has been used to determine the stereo-chemical course of phosphoryl transfer catalysed by rat liver glucokinase. The chirality of the product, D-glucose 6-[16O,17O,18O]phosphate was analysed by 31P n.m.r. spectroscopy. The reaction proceeds with inversion of configuration at phosphorus. The simplest interpretation of this result, which is the same as that observed with yeast hexokinase [Lowe & Potter (1981) Biochem. J. 199, 277-233], is that the phosphoryl group is transferred between MgATP2- and glucose in the ternary complex by an 'in-line' mechanism. It accords with the veiw that the kinetic differences between glucokinase and the other hexokinases arise from differences in rate constants and not from any fundamental differences in chemical mechanism.