title: Orthophosphate is a non-essential activator of Vigna radiata flavokinase.
abstract: The ATP-dependent phosphorylation of riboflavin to FMN by flavokinase from Vigna radiata was activated by orthophosphate (Pi) in a concentration dependent manner. Pi affected both the K(m) and Vmax, indicating that it is a non-essential, mixed type activator. The extent of activation by Pi was dependent on the cation (Mg2+ or Zn2+). Activation by other anions could be correlated to similarity to Pi in molecular size and structure. These observations suggest the presence of a binding site(s) for a phosphate-like anion on flavokinase.
mesh_terms: D000838:Anions; D002412:Cations; D004789:Enzyme Activation; D007887:Fabaceae / Q000201:enzymology*; D010710:Phosphates / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D010946:Plants, Medicinal; D013379:Substrate Specificity