Enzyme Reaction Rates at Limited Water Activities

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Science  22 Dec 1967:
Vol. 158, Issue 3808, pp. 1569-1570
DOI: 10.1126/science.158.3808.1569


A well-mixed powder consisting of dry urea and urease exposed to air containing discrete amounts of water vapor showed a release of carbon-14 dioxide above 60-percent relative humidity. The relative activity of urease followed the water-vapor adsorption isotherm of urease. The minimum amount of water required for the reaction observed was 1.3 moles per mole of side-chain polar groups of the urease protein.