K-PRIME

The apparent equilibrium constant K'. Concentrations in the equilibrium constant equation refer to the total concentrations of all forms of particular biochemical reactants. For example, in the equilibrium constant equation for the biochemical reaction in which ATP is hydrolyzed to ADP and inorganic phosphate: K' = [ADP][P_i]/[ATP], The concentration of ATP refers to the total concentration of all of the following species: [ATP] = [ATP^4-] + [HATP^3-] + [H₂ATP^2-] + [MgATP^2-] + [MgHATP^-] + [Mg₂ATP]. The apparent equilibrium constant is formally dimensionless, and can be kept so by inclusion of as many of the terms (1 mol/dm³) in the numerator or denominator as necessary. It is a function of temperature (T), ionic strength (I), pH, and pMg (pMg = -log₁₀[Mg²⁺]). (Definition from EcoCyc)

Source:http://www.biopax.org/release/biopax-level2.owl#K-PRIME