Urease catalytic 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. 

The composition, visible spectroscopy, and catalytic properties of urease have been reviewed by Blakeley and Zemer [25] and by Hausinger [2]. The urease from jack bean is typical of the enzymes from plants. It has a protein of relative... 

Evaluation of stability and catalytic properties of the immobilized system must take into account possible pH differences between the inner core of the fiber, where the reaction takes place, and the bulk of the feed solution. The production of compounds which alter the pH, like ammonia produced from urea via immobilized urease,48 and the partition properties in hollow fiber membranes can result in creating such pH gradients. Experimentally, these differences produce more or less pronounced shifts in the optimum pH dependence of enzyme activity relative to its free form dependence and thereby affect the activity of the enzyme at work.2 3 48... 

Zsrmoproteins.— Heat-labile proteins having catalytic properties. This group includes the important enzymes pepsin, papain, chymase, catalase, peroxidase, and urease. 

Biomimetic chemistry of nickel was extensively reviewed.1847,1848 Elaborate complexes have been developed in order to model structural and spectroscopic properties as well as the catalytic function of the biological sites. Biomimetic systems for urease are described in Section 6.3.4.12.7, and model systems for [Ni,Fe]-hydrogenases are collected in Section 6.3.4.12.5. 

The reaction carried out by urease is extremely specific. The mechanism of the reaction is not understood. No intermediates have been established and the enzyme requires no cofactors. Carbamate has been suggested as an intermediate, but it is possible that this is a secondary product. Very active urease has been obtained from bacteria. Although the properties of the proteins differ, the catalytic activities of urease from various sources appear to be very similar. 

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