Carbonic acid is a strong protonating agent

There is an important physiological demand, in order to sustain metabolic life-supporting processes, for fast in vivo acid-base reactivity. This is the protonation by acids−donors of a proton H⁺−of various bases−proton-acceptors −in the blood plasma. The most important acid here has long been thought to be the hydronium ion H₃O⁺. However, the concentration of H₃O⁺ in the blood plasma is very low. We have demonstrated that intact CA is a stronger acid^1-3 than acetic acid and even formic acid and can react as such before breaking down similarly to the hydronium ion while its steady-state concentration in the blood plasma is 70 times larger. For this reason, we suggest that CA should be the first physiological responder in rapidly establishing the equilibrium concentrations of acids and bases in the blood plasma. CA can also supply protons to fast physiological processes something that H₃O⁺ is deficient to do because of its very low concentration³.

References

1. Katrin Adamczyk, Mirabelle Prémont-Schwarz, Dina Pines, Ehud Pines and Erik T. J. Nibbering. Real-time observation of carbonic acid formation in aqueous solution Science, 326 (2009) 1690.
2. Dina Pines, Julia Ditkovich, Tzach Mukra, Yifat Miller, Philip M. Kiefer, Snehasis Daschakraborty, James T. Hynes, and Ehud Pines, How Acidic Is Carbonic Acid? J. Phys. Chem. B, 2016, 120 (9), pp 2440–2451.
3. Daniel Aminov, Dina Pines, Philip M. Kiefer, Snehasis Daschakraborty, James T. Hynes, and Ehud Pines, Intact carbonic acid is a viable protonating agent for biological bases, PNAS 2019 116 (42) 20837-20843.