Remarkable properties of Enzymes as catalysts

Enzymes display a number of remarkable properties when compared with other types of catalysts. The three most important are their high catalytic power, their specificity, and the extent to which their catalytic activity can be regulated by a variety of naturally occurring. Those three properties are as follows:-

1. Catalytic power:- 

                 Enzymes may increase the rate of reaction by as much as 10¹⁷ folds. There are not many examples where a direct comparison can be made between the rates of an enzyme-catalysed reaction and the reaction occurring under similar conditions of temperature, pH, etc., but in the absence of enzyme. This is because in the absence of enzyme the rates may be too low to be measured easily. In other instances, where enzymatic and non-enzymatic catalysts are compared, the former catalyse much higher rates and in some cases do so at significantly lower temperature. The optimum conditions for enzyme catalysis are usually moderate temperatures and pH values close to neutrality.

2. Specificity:-

                Most enzymes are highly specific both in the nature of the substrate they utilize and also in the reaction they catalyse. The range of specificity varies between enzymes. There are some enzymes that have relatively low specificities (bond specificity), e.g., certain peptidase, phosphatase and esterase, which will utilize peptide, phosphate ester, and carboxylate ester, respectively. Low specificity is more commonly encountered with degradative enzymes but is only very rarely observed with biosynthetic enzymes. The role of the former may be that of digestion, where wider specificity would be more economical. An intermediate set of enzymes show group specificity, e.g., hexokinase. This enzyme will catalyse the phosphorylation of a variety of sugars provided they are aldohexoses. However many enzymes show absolute or near-absolute specificity, in which they will only catalyse at an appreciable rate the reaction with a single substrate, e.g., urease will only catalyse the reaction with urea, or with very similar analogues at very lower rates.

3.Regulation:-

                The third important property of enzymes is that their catalytic activity may be regulated by small ions or molecules or by some change in their covalent structure. A good example of these effects is provided by the enzyme phosphorylase, which catalyses the first step in breakdown of glycogen in skeletal muscles. This is an important enzyme that enables the carbohydrate reserves to be degraded in order to generate ATP required for muscle contraction. The onset of muscle contraction is triggered by release of  Ca²⁺ from the sarcoplasmic reticulum and this also brings about activation of phosphorylase to ensure the continued production of ATP.