Volume 2, Number 1/2, p. 25-37
Philippa M. Wiggins
Auckland, New Zealand.
Enzyme reactions and two-state water
An attempt is made to analyse the rôle that two-state water might play in biochemical processes. The two liquid polymorphs, which are in rapidly exchanging equilibrium, have different densities and hydrogen bond strengths and must, therefore, have different chemical and physical properties. A solute added to two-state water creates instantaneous osmotic pressure gradients across interfaces between unlike contiguous domains. The consequence is a local displacement of the water equilibrium which has a limiting thermodynamic cost. Surfaces add to the complexity with many osmotic forces operating on the same surface water. Osmotic responses involve vectorial processes which are often self-limiting and have many of the properties of enzyme reactions. Mechanisms are suggested for gating of channels, ATP hydrolysis as a reaction coupled to cation pumps, synthesis of ATP, peptides and polynucleotides and the action of calcium-activated proteases and motor molecules. The crucial rôles played by small solutes, especially ions (Ca2+, Mg2+, Na+, K+ and univalent anions) are emphasised. A possible mechanism for the origin of chirality is discussed and illustrated by the synthesis of poly-L-lysine from a racemic mixture in a silica gel.
Keywords: ATP hydrolysis, ions and enzyme activity, micro-osmosis gated ion channels, origin of chirality.