Fig.2. Decline in the phospho-protein concentration with distance from the cell membrane at different values of the parameter . The parameter is determined by the ratio of the characteristic times of diffusion and the phosphatase reaction (²=K_pxL²/D, where L is the cell radius, K_p=V_max,p/K_m,p is the observed first-order rate constant of the phosphatase and D is the protein diffusion coefficient). The decline, p(x)/p(1), is calculated as the ratio of the concentrations of the phosphorylated form at distance xL from the cell center and at the plasma membrane, where x=1. Reproduced with permission from Kholodenko (2002).