Introduction of Enzyme

Introduction:

Enzymes are the natural biocatalyst which permits the Endogenous biological reactions to occur rapidly through the well-defined pathway. They are found in almost all creatures of nature from a minute microorganisms ( Virus, bacteria) to well-defined human beings. They are located in cytoplasm,mitochondria,tissues and cells. Enzymes are composed of one or more polypeptide organized in a 3D structure. Some enzymes contains only the peptide chain and contain no chemical groups ie. pancreatic ribonuclease. Some enzymes need Co-factor eg: Zn⁺⁺, Fe⁺⁺and Mn⁺⁺ or some enzymes complex require co-enzymes9Vitamins) . Tthe tightly bound coenzyme or cofactor is called prosthetic group.

Holoenzyme→ Apoenzyme + prosthetic group

( functional group) (protein part) ( nonprotein part coenzyme/ cofactor)

The coenzyme and cofactor are stable on heating whereas protein part of an enzyme is denaturated by heat. Enzymes accelerate the rate of chemical reactions without loss in the process.

Thus enzymes may be defined as biocatalyst synthesized by living cells.They are protein in nature,colloidal and thermolabile in character, and specific in their action.

Measurement of enzyme activity:

The enzyme activity is measure in turn over number ie. a number of substrate molecules transformed per minute by the single molecule of enzymes and the enzyme activity are measured in an international unit (IU) or (SI) unit.

a) One IU: It is defined as the one mole of substrate transformed into a product by a single molecule of enzyme in one minute under defined conditions ( pH= 7, T= 25 , P= 1 atm)

b) One SI unit: It is defined as the one mole of the substrate is transformed into a product by a single molecule of an enzyme in one second under the specific condition.

c) One katal: It is defined as the number of substrates converted into product per second under defined conditions.

Energy of activations:

Some amount of energy must be applied to reactant particles to convert into a product. The minimum amount of energy that is required to convert reactants into the product is known as threshold energy(Et) . At ordinary conditions, the energy associated with the reactant particles is known as( E_av)ie activation energy. The excess amount of energy that must be applied to convert the reactant particles into the product is known as activation energy.

Difference between enzyme and catalyst:

Enzyme technology:

Enzymes are mostly the proteinous bio-catalyst produced by living organisms ( plants ,animals, and microorganisms) in the small quantity that function in a highly selective manner and are involved in the conversion of one molecule substrate to another molecule of a product without themselves undergoing any changes.

Enzyme technology is an interdisciplinary field that has had a broad impact on biotechnology,synthetic chemistry pharmaceutical development, and agriculture. In addition to fundamental enzymology, enzymes are used routinely in the development of new biologically active compounds and their intermediate, the preparation of materials with unique and functional properties and the evolution of novel processes for synthesizing and purifying enzyme- derived products. The repertoire of biocatalysts with highly selective properties that function under rigorous environment.

The present focus of the enzyme Technology Group is on:

a) The study of chitin deacetylases from Fungi:

At present ,chitosan is produced by the thermochemical deacetylation of chitin. An alternative or complimentary procedure exploiting the enzymatic deacetylation of chitin could potentially be employed, especially when a controlled, nondegradtive and well-defined process is required.

b) The study of enzyme from psychrophilic microorganisms with two main objectives:

The first concerns the biotechnological capacity of these enzymes to develop , when possible ,new biocatalysts which have high specific activities at low and moderate temperature as well as new specificities. The second is fundamental and aims at defining the rules governing the molecular adaptations of cold enzymes produced by psychrophilic microorganisms.

c) The isolation ,cloning, and characterization of restriction endonucleases and DNA methyltransferases.

d) The downstream processing of enzymes:

Modern enzyme isolation technology can yield novel diagnostic and medically significant enzymes. There are several high - value enzymes that are required in large quantities. Purification system based on dye and other affinity absorbents, which use both low and high-pressure liquid chromatography,offer an attractive alternative to the conventional techniques employed to date. It is economically important to test in detail the potential applicability of affinity absorbent in large -scale enzyme isolation.

Nomenclature and Classification of Enzymes:

Enzymes are generally named after adding the suffix -ase to the name of the substrate .eg: enzymes acting on nucleic acid are called nuclease and the enzyme which hydrolyses the peptide is called peptidase. However few exception such as Trypsin,pepsin and chymotrypsin are still in used. Few enzymes exist in their inactive form called as proenzymes and zymogens.

The International Union of biochemistry (IUB) explained a nomenclature system based on chemical reaction type and reaction mechanism. According to this system, enzymes are classified into six main classes and each enzyme is characterized by an enzyme code number (ECN) with 4 figures (digits) separated by points eg: Hexokinase (ECN)= 2.7.1.1

the first digit= indicates the main class

second digit= indicates the type of group involved in the reaction ( subclass)

Third digit= The substrate on which the group acts( sub- sub class)

fourth digit= The serial number of enzyme

Briefly, four digits characterized the class, sub class,sub- sub classes and the serial number of particular enzymes . There are mainly six classes of enzymes which are given as follows:

1) Oxidoreductases

2) Transferases

3) Hydrolases

4) Lyases

5) Isomerases

6) Ligases

1) Oxidoreductases:

In this class, the enzymes which are involved in the oxidation and reduction of their substrate are included , they transferred H+ or electron from one substrate to another. eg: alcohol dehydrogenase

alcohol dehydrogenase

alcohol → aldehyde + hydrogen ion.

2) Transferases:

In this class, the enzymes which are involved in the transfer of the particular group from one substitute (donor) to another substrate (acceptor) are included. Hexokinase is the example of enzyme included under this class. the generally alkyl group, the acyl group, and phosphate group transfers.

hexokinase

Glucose → Glucose 6- phosphate

3) Hydrolases:

In this class, the enzymes which are involved in the splitting or cleavage of C-O, C- N and C-C by the addition of water molecules are involved . The different types of bonds hydrolysed by the hydrolases enzymes are the glycosidic bond ,peptide bond, and ester bond. example. Glucose 6- phosphatase, Glycosidase.

glycosidase

Maltase → αD Glucose +αD Glucose

4) Lyases:

The enzyme which is involved in the removal of small molecule from a large molecule are involved in this class.eg: Fumarase,decarboxylase

5) Isomerase

The enzymes which are involved in isomerization of substrate ie: redistribution of atom or chemical group within a molecule are involved in this group, eg; glucose -6 phosphate isomerase, epimerase,ribose 5- phosphate isomerase.

6) Ligases:

In this class the enzymes which are involved in going together of 2 substrates usually C-O, C-C and C-N are included in this group eg: aminoacyl t-RNA synthetase, glutamine synthetase.

On the basis of structural organization the enzymes are classified into following three groups:

1) monomeric enzyme

2) Multimeric enzyme

3) Isomeric enzyme

1) Monomeric:

The enzymes which contain only one polypeptide chain are called monomeric enzymes. The occurrence of these enzymes is least in nature .eg. pancreatic ribonuclease.

2) Multimeric:

It contains many subunits of enzymes and performs the sequential reactions eg: pyruvate dehydrogenase which consists of three enzymes:

a) pyruvate decarboxylase

b) Dihydrolipoyl transacetylase

c) Dihydrolipoyl dehydrogenase

3) Isoenzymes:

They are the physically distinct form of some enzymes and catalyzed the same chemical reactions. They differ from each other structurally ,electrophoretically and immunologically . Lactate dehydrogenase which has 5 isoenzymes namely LDH,LDH2, LDH3,LDH4, LDH5 . Similarly, malate dehydrogenase has two isoenzymes.