Testing cosolvent cryoenzymology on multi-enzyme systems.

Fluid mixed solvents appear to supply an effective tool for investigation of enzyme catalysis at subzero temperatures. Labile reaction intermediates may be stabilized, characterized and separated. Cycling of reaction processes and side reactions can be slowed or stopped to permit single turnover of individual molecular events, and kinetic response to temperature and other physical parameters can provide dynamic and thermodynamic analysis of single enzyme systems. Multienzyme systems can furnish reliable probes of potential, limitations and possible procedural artefacts of the method. Amply explored examples are supplied by the studies of two components of the soluble camphor hydroxylase and the hepatic R450LM2 in solution and in the subcellular microsomal organelles, to reveal labile single enzyme compounds and multienzyme processes.