Enzymes are capable to react with only one of two optical isomers. Example:
Enzymes are capable of catalysing the reaction of a structurally related group of compounds. Example: Lactate dehydrogenase catalyses the inter-conversion of pyruvic acid and lactic acids and also a number of other related compounds.
Enzymes are capable of acting on only one substrate. Example: Urease acts only on urea to produce ammonia and CO2.
Enzymes are highly specific in two ways—first in the reaction catalysed and second in the choice of reactants called substrates.
Turnover number is defined as the number of substrate molecules converted into product per unit time when the enzyme is fully saturated with substrate. It depends upon its molecular weight. Example: Transfer of Carbon dioxide from tissues into blood and then to the alveolar air would be less complete in the absence of an enzyme. Carbonic…
Enzymes are sometimes considered under two broad categories: Chemically, the enzymes may be divided into two categories: The functional unit of enzyme is known as holoenzyme, which is oft en made up of apoenzyme (the protein part) and coenzyme (non-protein part). The term prosthetic group is used when the non-protein part (tightly) covalently binds with the apoenzyme. The coenzyme or…
1836 – Berzelius coined the term catalysis. 1878 – Kuehne worded the word enzyme. 1883 – Buchner isolated enzyme from yeast zymase. 1926 – James Sumner isolated from Jack Beans. He got noble prize in 1940. 1930 – Northrop crystallised proteolytic enzyme from gastrointestinal tract.
In mammalian cells, including those of human beings, DNA-dependent RNA polymerase first synthesises precursor RNA in the nucleoplasm. This precursor is then degraded by a nuclear nuclease to mRNA that is then translocated to the cytoplasm, where it becomes associated to the ribosomal system. This precursor RNA constitutes the fourth class of RNA molecules and…
The abundance of RNA n the cytoplasm and its role in protein synthesis suggested that the genetic information of nuclear DNA is transmitted to an RNA which functions at the sites of protein synthesis. In 1961, the two Nobel laureates Francois Jacob and Jacques Monod postulated that control of protein formation, at least in certain…