ENZYMES PART -1

 Enzymes are biocatalyst. These are required in small amounts in a chemical reaction. Enzymes convert substrates into products without being utilized in the reaction. Enzymes were considered to be proteins, but ribozymes are enzymes that are made of RNA molecules.  Antibodies that have catalytic activity are called abzyme.

 FASTEST ENZYMES AND TURNOVER RATE

 Enzymes convert substrate into  product in a second this is called turnover rate.

 Some of the fastest enzymes are carbonic anhydrase that converts 600000 molecules of carbon dioxide and water in carbonic acid in a second,this is fastest known enzyme.

 Catalase converts 93000 molecules into the product, then being beta-galactosidase 200 molecules/second, trypsin, and tyrosinase also have good turnover rate.

 The enzymes are specific catalyst that is, they can convert only their substrate into product. Glucose oxidase can convert only beta D glucose

 Group specific enzyme convert a group of the substrate into products example Alkaline phosphatase that removes the phosphate group from a variety of substrate.

CLASSIFICATION OF ENZYMES

There are six main classes of Enzymes. These are classified on the basis of reaction to carry out.

 Oxidoreductases are the enzymes that carry out oxidation or reduction reaction

 Transferases are the enzymes that transfer one atom or group

 Hydrolases that carry out hydrolysis

 Lyases they remove a group

 Isomerases that bring about isomerization reaction

 Ligases this enzyme join molecules

 Secondary classes of enzymes have been formed for example oxidoreductases  may have secondary classes  based on  molecules that have donated hydrogen or electrons

 Tertiary classes of enzymes of oxidoreductase are based on hydrogen or electron receptor is involved in oxidation-reduction reactions.

The primary, secondary, and tertiary classes are denoted by numeric value.

^Thus lactate dehydrogenase with the EC number 1.1.1.27 is an oxidoreductase (indicated by the first digit) with the alcohol group of the lactate molecule as the hydrogen donor (second digit) and NAD+ as the hydrogen acceptor (third digit), and is the 27th enzyme to be categorized within this group (fourth digit)^1.

 

ENZYME ACTIVITY

 Enzyme substrate activity enzyme has an active site, in its three-dimensional structure as enzymes are made of proteins and proteins are folded in a specific way so enzyme may have a specific site for binding with the substrate. This specific site is called an active site. Enzyme and substrate bind at this site, this activity was explained by Emil Fischer through his lock and key hypothesis. According to this hypothesis, the enzyme has a specific active site that has conformation such that only the substrate can bind with it.

REPRESENTATION OF ENZYME-SUBSTRATE REACTION

 However, it was later proved by x-ray crystallography experiments the episode o flexible and changed after binding with the substrate this was then explained by the induced fit model given by Daniel Koshland where the enzyme's active site modifies itself to accurately bind with its substrate.

HOLOENZYME, APOENZYME, COFACTORS, COENZYME, METALLOEZYMES

 Enzymes not only have a protein structure(apoenzyme) but it has some accessory molecules that are involved in their activity these molecules are called a cofactor.

HOLOENZYME

 The enzyme along with the cofactor is called a holoenzyme. So, holoenzyme has two parts an apoenzyme enzyme that is a catalytic part that is mainly made of a protein, the cofactor is the necessary part which may be a coenzyme, a prosthetic group, or metal ion. So, the cofactors are two types organic or inorganic.

Apoenzyme +cofactor = holoenzyme

 Organic cofactors are mainly coenzymes such as NAD, NADPH.

 Inorganic cofactor can be a metal ion, Such enzymes are called metalloenzymes.

 Prosthetic group are cofactors that are tightly bound to apoenzymes to form holoenzyme.

References

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4692135/