title: Life and the outer planets. II. Enzyme activity in ammonia-water systems and other exotic media at various temperatures.
abstract: Enzyme activities are customarily measured in aqueous solutions. Activity and thermodynamic parameters are based upon behavior in these solutions although they in no way represent the highly structured internal surface system of the cell. Actual environmental limits for enzyme action may be greater than generally assumed. Peroxidase, catalase, urease and amylase retain activity in drastically modified aqueous and nonaqueous media, including aprotic solvents. Examples include formic acid, methanol, formamide, nitromethane, 10 M LiCl and 15 M aqueous ammonia. Temperatures as low as 225-233 degrees K permit activity in some media. Ammonia-rich environments are compatible with some forms of terrestrial life. Enzyme activity in these exotic media and conditions is relevant to chemical evolution on Jupiter and similar planetary systems.
authors.affiliation: Department of Botany, University of Hawaii, Honolulu, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Siegel
authors.forename: T W
authors.initials: TW
authors.lastname: Speitel
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D002374:Catalase / Q000737:chemistry; D003080:Cold Temperature; D003470:Culture Media / Q000737:chemistry; D004798:Enzymes / Q000737:chemistry*; D019418:Evolution, Chemical; D018559:Exobiology; D006139:Guaiacol / Q000737:chemistry; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000737:chemistry; D008697:Methane / Q000737:chemistry; D009195:Peroxidase / Q000737:chemistry; D016083:Planets; D014510:Urease / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D003470:Culture Media; D004798:Enzymes; D014867:Water; D006139:Guaiacol; D000641:Ammonia; D006861:Hydrogen Peroxide; D002374:Catalase; D009195:Peroxidase; D014510:Urease; D008697:Methane