Spinach thylakoids were transferred into a reverse micellar phase (detergent CTAB, 1-hexanol and n-octane (CHO)). The macrocomplexes transferred into CHO displayed ion-dependent and methanol-enhanced ATPase activities similar to the membrane-bound enzyme in aqueous buffer. Both latent and methanol-modulated enzyme activities were highly dependent on the amount of water present, e.g. reducing water content from 7.2%, to 3.6% decreased the specific ATPase activity 3 fold. Decreasing concentrations of water in CHO increased the fraction of bound water as shown by ¹H-Nuclear Magnetic Resonance. However the observed water-dependent ATPase activities did not fully follow the measured activity of water in the low water system, indicating that other regulatory factors are involved.