Description
Glycerol kinase from E. coli (glpK) catalyzes the ATP-dependent phosphorylation of glycerol to produce sn-glycerol-3-phosphate (G3P), the first and rate-limiting step in the utilization of glycerol. In the presence of glycerol, glpK is stimulated by interaction with the membrane-bound glycerol facilitator. In the presence of glucose, glpK activity is allosterically inhibited by fructose-1,6-bisphosphate (FBP) of the glycolytic pathway. Under physiological conditions, the enzyme is in an equilibrium between the active dimer and the inactive tetramer. FBP binds to and stabilizes the inactive form, therefore shifting the usage of glycerol metabolic pathway to glycolytic pathway. GlpK is a member of a superfamily of ATPases that includes actin, hexokinase and the heat shock protein hsc70. Although these proteins are dissimilar in amino acid sequence and function, they share similar tertiary folds and likely the same catalytic mechanism. The enzyme activity was measured using a phosphatase-coupled kinase assay