Urease molecular properties

Enzymes are proteins of high molecular weight and possess exceptionally high catalytic properties. These are important to plant and animal life processes. An enzyme, E, is a protein or protein-like substance with catalytic properties. A substrate, S, is the substance that is chemically transformed at an accelerated rate because of the action of the enzyme on it. Most enzymes are normally named in terms of the reactions they catalyze. In practice, a suffice -ase is added to the substrate on which die enzyme acts. Eor example, die enzyme dial catalyzes die decomposition of urea is urease, the enzyme dial acts on uric acid is uricase, and die enzyme present in die micro-organism dial converts glucose to gluconolactone is glucose oxidase. The diree major types of enzyme reaction are ... 

Much uncertainty reigned over the nature of proteins, the best known of which were hemoglobin, the digestive enzymes, and later, insulin. Properties of individual amino acids and the peptide bond were studied early in this century, but it was not until urease was crystallized by Sumner1 in 1926, followed by the isolation of other pure enzymes, that it was finally accepted in the 1930s that enzymes were proteins and that their catalytic properties were not the function of some adsorbed low molecular weight entity. Somewhat later, towards the end of the 1930s, coenzymes were isolated and their roles established. 

At molecular level, the manifestations of the biological activity appear in specific biochemical reactions, conformational behavior, and dynamical properties of biomolecules. Experimental studies of various partially hydrated enzymatic proteins show that their activity accelerates rapidly at some critical hydration levels. Onset of the enzymatic activity of urease occurs at 0.15 g/g [469]. In the presence of chymotrypsin, the acylation reaction is undetectable at hydrations /i< 0.12 g/g, but its rate grows sharply above this critical hydration level [470]. The rate of enzymatic activity of glucose-6-phosphate dehydrogenase, hexoki-nase, and fumarase becomes detectable and start to increase sharply at hK 0.20 g/g, whereas this critical hydration is about 0.15 g/g for phosphoglucose isomerase [471]. Enzymatic activity of lysozyme can be detected only when hydration level achieves h 0.20 g/g [472, 473] (see Fig. 92). 

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