Chemistry and biology of deoxy-myo-inositol phosphates: stereospecificity of substrate interactions within an archaeal and a bacterial IMPase.

Six enantiomerically pure myo-inositol-monophosphates, including four deoxygenated analogues, have been synthesized by employing catalytic asymmetric phosphorylation methodology. These compounds were then evaluated as substrates for the direct interrogation of the stereospecificity of enzyme-substrate interactions with two inositol-monophosphatases (IMPases), one of which (from Archaeoglobus fulgidus) is characterized by an X-ray crystal structure with its substrate (d-I-1P) bound. The kinetic results lead to the finding that certain hydroxyl group contacts are actually destabilizing, while others have little effect. These new probes also allow a prediction of the active site binding mode of the substrate for the Escherichia coli IMPase for which no crystal structure exists.