Enzymes, hydrolytic

While all these enzymes hydrolytically cleave a-glycosidic bonds of sialic acids, another type of sialidase has been discovered, which can also hydrolyze these linkages but preferably forms sialic acid linkages under physiological conditions in the presence of suitable acceptors. These are the /rans-sialidases, occurring in parasites, and a... 

J.R. Monte, M. Brienzo and A.M.E Milagres, Utihzation of pineapple stem juice to enhance enzyme-hydrolytic efficiency for sugarcane bagasse after an optimized pre-treatment with alkaline peroxide. Appl. Energ. 88,403-408 (2011). 

Adenosine deaminase from calf intestinal mucosa, the most widely studied enzyme, hydrolytically deaminates, in addition to adenosine, some other natural and synthetic nucleosides and also dehalogenates 6-halopurine ribosides. Many studies have been carried out to define the contribution of purine and ribose moieties in the binding of substrate and to help prepare effective inhibitors of the enzyme. - ... 

Hydrolases. Enzymes catalysing the hydrolytic cleavage ofC —O, C —N and C —C bonds. The systematic name always includes hydrolase but the recommended name is often formed by the addition of ase to the substrate. Examples are esterases, glucosidases, peptidases, proteinases, phospholipases. Other bonds may be cleaved besides those cited, e.g. during the action of sulphatases and phosphatases. 

Since trypsin is a mixture, it has no well-defined optimum pH. It should also be noted that trypsin is the only hydrolytic enzyme which is at all active in alkaline solution. 

Inspired by the many hydrolytically-active metallo enzymes encountered in nature, extensive studies have been performed on so-called metallo micelles. These investigations usually focus on mixed micelles of a common surfactant together with a special chelating surfactant that exhibits a high affinity for transition-metal ions. These aggregates can have remarkable catalytic effects on the hydrolysis of activated carboxylic acid esters, phosphate esters and amides. In these reactions the exact role of the metal ion is not clear and may vary from one system to another. However, there are strong indications that the major function of the metal ion is the coordination of hydroxide anion in the Stem region of the micelle where it is in the proximity of the micelle-bound substrate. The first report of catalysis of a hydrolysis reaction by me tall omi cell es stems from 1978. In the years that... 

The antibacterial effectiveness of penicillins cephalospotins and other P-lactam antibiotics depends upon selective acylation and consequentiy, iaactivation, of transpeptidases involved ia bacterial ceU wall synthesis. This acylating ability is a result of the reactivity of the P-lactam ring (1). Bacteria that are resistant to P-lactam antibiotics often produce enzymes called P-lactamases that inactivate the antibiotics by cataly2ing the hydrolytic opening of the P-lactam ring to give products (2) devoid of antibacterial activity. 

Hydrolytic enzymes such as esterases and Upases have proven particularly useful for asymmetric synthesis because of their abiUties to discriminate between enantiotopic ester and hydroxyl groups. A large number of esterases and Upases are commercially available in large quantities many are inexpensive and accept a broad range of substrates. 

It is generally beheved that selectivity of hydrolytic enzymes strongly depends on the proximity of the chiral center to the reacting carbonyl group, and only a few examples of successful resolutions exist for compounds that have the chiral center removed by more than three bonds. A noticeable exception to this rule is the enantioselective hydrolysis by Pseudomonasfluorescens Hpase (PEL) of racemic dithioacetal (5) that has a prochiral center four bonds away from the reactive carboxylate (24). The monoester (6) is obtained in 89% yield and 98% ee. 

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