Astroenzymology - the environmental limits of enzyme activity

Roy Daniel, Richard B. Hoover, Alexei Y. Rozanov, Roland R. Paepe
2003 Instruments, Methods, and Missions for Astrobiology V  
Using organisms from extreme terrestrial environments as models for extraterrestrial life may lead us to underestimate the range of environments that life may inhabit. An alternative approach is to inspect the range of conditions over which crucial biomolecules might function. Recent investigations of enzyme activity suggest that they have the potential to function over a wider range of environmental conditions than expected. Although the upper temperature limit for enzyme stability is unclear,
more » ... some enzymes are active up to 130 o C. The evidence is that that the instability of enzymes is a functional requirement, rather than because of any restraint on achieving higher stability. There is no evidence that enzyme activity ceases at low temperatures; it declines in a predictable manner to the lowest temperature at which it has been possible to make measurements, -100 o C. It has been generally accepted that dehydration stops enzyme activity but this acceptance may have arisen partly from the technical difficulty of assessing enzyme activity without a fluid medium for diffusion. Experiments using anhydrous organic solvents or gas phase substrates suggest activity occurs in enzymes at very low hydration. Apart from the obvious implications for life under restricted hydration, it should be noted that the results suggest that the minimum size requirement for cells may be less than has been thought.
doi:10.1117/12.457322 fatcat:eaaazcxlozcytjpvpijg4mrd2y