Catalytic potency

There are other ways to appreciate the catalytic potency of enzymes in addition to that provided above. A second way to understand the same point is to accurately measure ratios between rates of enzyme-catalyzed reactions and the corresponding uncatalyzed reactions under the same conditions, a refinement of the qualitative argument just made. These ratios are frequently not easy to obtain since the rates of the uncatalyzed reactions may be so slow as to make them exceedingly difficult to measure. Nonetheless, a number of these ratios are known and they typically vary between abont 10 (one thousand) and 10 (one quadrillion), truly enormous values. To help understand just how large 10 is, consider a chemical reaction begun at the time of the creation of our solar system whose progress would be barely detectable at the present day. That same reaction would be nearly complete in 1 minute if catalyzed IQi -fold. 

Fischer, L., Bromann, R., Kengen, S.W.M., de Vos, W.M. and Wagner, F. (1996) Catalytical potency of b-glucosidase from the extremophile Pyrococcus furiosus in glucoconjugate synthesis. Biotechnology 14, 88-91. 

The specific activity of the enzyme was determined in 0.15M lactose solution (0.02M phosphate buffer, pH 7-0). The activity of the enzyme was expressed in terms of units of activity per mg of enzyme. A unit of activity was defined as a p mole of glucose produced per minute. The soluble lactase activity following affinity chromatography purification was 37-1 units/mg. This represented a 4 fold increase in catalytic potency over the specific activity of the crude enzyme preparation (8.9 units/mg). 

Enzyme Assay Procedure. The catalytic potency of the immobilized g-galactosidase was determined in a plug flow reactor ( 9). Glucose liberated by the catalytic activity of 3-galactosi-dase on lactose was determined by the glucose oxidase-chromogen method (21 ) with some modifications. 

The influence of the anion in contributing to the catalytic potency toward the IL can be rationalized with this mechanistic proposal. The catalytic activity of ILs is determined by the feasibility of hydrogen bonding between indole and HSO, MeSOj", and BF anions through six-/five-membered chair-/envelop-like cychc structures 11-13 and 14-16 (Fig. 12.33) [22]. 

The key features of DNA polymerase III are its catalytic potency, its fidelity, and its processivity. It is able to catalyze the addition of 10 bases per second, compared to only about 10 per second for DNA polymerase I, with an error frequency of about 1 10 -10. One of the unique features of DNA polymerase III is its ability to continuously synthesize very long (thousands of bases) stretches of DNA, unlike DNA polymerase I. This is a consequence of its processivity the P2 sliding clamps ensure that it remains bound to the template strand DNA. In contrast, DNA polymerase I, without a sliding clamp, is much more likely to dissociate from the template strand after synthesis of short (tens of bases) stretches of DNA. 

Iwabuchi with coworkers designed a series of 4-silylo)yproline derivatives with a view to confer lipophilic properties to the proline motif and thereby secure a basis for the catalytic activity growth. They found that (2S,4R)- and (2R,4R)-4-silylo yprolines 30 or their BU4N salts 31 (Figure 10.3) exhibit enhanced catalytic potencies to enantioselectively convert a-sym-metric keto-aldehyde 36 to bicyclo[3.3.1]-type products 37 or ent-37 with opposite enantiopreferences and different enantiocontrolling proficiencies (Scheme 10.8). Unexpectedly, the use of carbojylate (2S,4R)-31 (5 mol%) markedly enhanced the aldolisation rate to complete the reaction in 3 h at room temperature and furnish 77% 37 with 98% diastereomeric excess and... 

Gadekar L. S Katkar S. S., Vidhate K. N., Arbad B. R., Lande M. K., Babasaheb A. Modification, characterization and catalytic potency of modified natural... 

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