Glycerol kinase catalyses the phosphorylation of the symmetrical substrate, 2-dexoy-2-flurooglycerol, by ATP to an asymmetric product, 2-deoxy-2-fluoro-sn-glycerol 3-phosphate. The stereospecificity of the enzymic reaction was extablished by unambiguous chemical synthesis of 2-deoxy-2-fluoro-sn-glycerol labelled with 2H at C-1, followed by glycerol kinase-catalysed phosphorylation and isolation of the labelled phosphate. The configuration of the 2H-labelled phosphate was determined by n.m.r. spectroscopy. This enzymic phosphorylation of 2-dexoy-2-fluoroglycerol is absolutely stereospecific in the same sence as that of glycerol, with fluorine replacing the C-2 hydroxy group. The behaviour of fluorine as a hydroxy analogue in directing the stereospecific course of the enzyme reaction is relevant to the use of the fluorine atom of fluoro analogues of substrate as a reporter group for hydroxy-binding sites of enzymes.
