Enzymatic Mechanisms of Phosphate and Sulfate Transfer

Many biological molecules contain phosphate or sulfate, and the enzymatic reactions that transfer these groups play important roles in metabolism. DNA and RNA are phosphate diesters, while many intermediates in metabolism exist as phosphate monoesters. Phosphorylation of proteins is an important control mechanism. While triesters are not naturally occurring biological molecules, enzymes have evolved to hydrolyze these man-made toxic compounds. ATP and similar molecules contain phosphoanhydrides, which liberate considerable free energy upon their hydrolysis and, thus, provide the energy needed for muscle movement and the biosynthesis of other bonds. Esterification with sulfate serves to solubilize molecules to aid in their excretion, and sulfate monoesters are found among many classes of natural products, possibly aiding in transport. In this review we will briefly present what is known about nonenzymatic phosphate and sulfate transfers, and then we will discuss the kinetic and chemical mechanisms of enzymes that catalyze similar transfers.