ADK and schizophrenia: Other factors may influence ADK activity in schizophrenia patients such as the local availability of its co-factor Mg2+ (Spychala et al., 1996; McNally et al., 1997), the relative expression of the two ADK isoforms (McNally et al., 1997), or the occurrence of any mutations altering the active site, the substrate- or co-factor binding site, or the overall folding of the enzyme.