| Protein tyrosine phosphatase-like myo-inositol phosphatases (PTPLPs) remove phosphoryl groups from phosphorylated myo-inositols (IPs) via largely ordered pathways. To understand the substrate specificity of this enzyme family, a simple method has been developed to produce pure, less-phosphorylated IPs that involves the hydrolysis of InsP6. The less-phosphorylated IPs were utilized to characterize the binding affinity and apparent kinetic parameters of a representative PTPLP. Finally, the structure of a PTPLP from Desulfovibrio magneticus and its hydrolytic pathway were determined. Main-chain conformational differences within the substrate binding site give rise to its unique InsP6 dephosphorylation pathway and has allowed for the identification of structural determinants that give rise to its specificity for the C4 phosphoryl of Ins(1,2,4,5,6)P5. Understanding how the number and nature of contacts in each of the phosphoryl binding sites control specificity will ultimately allow us to engineer PTPLPs with any desired substrate specificity. |
