||"Carbon dioxide exists in four different chemical forms which are interconverted via the following four reactions (see Edsall and Wyman, 1958 Kern, 1960, see link At neutral pH the uncatalyzed hydration-dehydration of CO2 by reactions (1) or (2) is a slow process having the following approximate rate constants at 25°C: k1=3.7×10^-2s^-l k-1=14s^-1 k4=8.5×10^3liter×mol^-1×s^-l and k-4=2×10^-4s^-1. The k2's and k3's, on the other hand, are essentially instantaneous, i.e. diffusion limited. Carbonic anbydrase at concentrations of about 2 mg/ml (60µM) increases the hydration-dehydration of CO2 by about 10^5. When present, CA usually occurs in such high concentrations that the hydration-dehydration of CO2 is not the rate-limiting step in biological transport processes (Maren, 1967 Maren et al., 1976)."