Rate constant of the reaction HCO3- →OH- + CO2 in the absence of carbonic anhydrase

Value 8500 liter×mol^-1×s^-l
Organism Generic
Reference Gutknecht J, Bisson MA, Tosteson FC. Diffusion of carbon dioxide through lipid bilayer membranes: effects of carbonic anhydrase, bicarbonate, and unstirred layers. J Gen Physiol. 1977 Jun69(6):779-94. p.781 top linePubMed ID408462
Comments "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)."
Entered by Uri M
ID 106118