Bio-molecules Enzymes Preparation and Properties
→ Enzymes are biocatalyst. These are synthesised by living cells. First of all, J. Przelius discovered enzyme Amylase. The name ‘enzyme’ was given to these biocatalysts by W. Kuhen. First of all, J.B. Summner in 1926, synthesise enzyme urease in laboratory in crystalline form and tells that enzymes are proteins molecules.
→ Definition of Engymes : Meyer beck defines enzymes as “Enzymes are simple or conjugated proteins which acts as specific catalysts”. Or “Enzymes are complex carbon compounds which catalyses biological reaction without itself undergoing any change.”
Characteristics of Enzymes :
- Generally all enzymes are colourless and soluble in dilute solutions of salts and water.
- Chemically, enzymes are made up of proteins.
- Enzymes are not utilised in a reaction. Thus’, the same enzyme can take part in a reaction with similar substrate.
- Very low quantity of enzyme is required in any reaction.
- Enzymes increase the rate of reaction by decreasing activation energy for the reaction.
- Their presence can increase the reaction rate by 1020 times.
- Enzymes only increased rate of reaction, there is no effect of enzymes on direction and equilibrium.
- Enzymes are specific in nature i.e., one kind of enzyme can catalyse a particularbype of reaction.
- Example, amylase enzyme only catalyses glucose hydrolysis but sucrose do not catalyse.
→ The activity of enzymes can be controlled orslowed down by some organ and inorganic substances.
- Enzymes are more active at 310 K temperature and normal pH (6-8).
- High temperature, ultraviolet rays, acid, high salt concentration and basic reactants cause denaturation of enzyme. This ceases the activity of the enzyme.
- Some artificial substances shows catalyticactivity like enzymes. These are known as artificial enzymes.
Nomenclature and Classification of Enzymes :
→ Till now about 3000 enzymes are known. Out of these approximately 300 enzymes are produced commerically. According to modern nomelAclature, enzymes are named by adding suffix ‘àse’ after the name of substrate on which enzyme works.
- The enzyme that changes lipid into amino acids is known as protease. the enzyme that catalyses hydrolysis of maltose into glucose is named as maltase.
- I.U.B. (International Union of Biochemistry) in 1965 classified enzymes in to six groups as follows.
Classification of enzymes :
|Group of enzyme||Catalyzed reaction||Examples|
|Oxido-reductase||Transfer of hydrogen and oxygen atoms one substrate to another.||Dehydrogenases|
|Transferases||Transfer of a specific group (a phosphate or methyl etc.) from one substrate to another.||Transaminase Kinases|
|Hydrolases||Hydrolysis of a substrate.||Estrases Digestive enzymes|
|Isomerases||Change of the molecular form of the substrate.||Phosphohexo isomerase, Fumarase|
|Lyases||Nonhydrolytic removal of a group or addition of a group to a substrate.||Decarboxyl ases, Aldolases|
|Ligases (synthetases)||Joining of two molecules by the formation of new bonds.||Citric acid synthetase|
Table : Functions of some Enzymes
|Where it is made||Where is works||Enzyme||Substrate||Products|
|Stomach cells||Stomach||Protease||Protein||Amino acids|
|Liver||Small intestine||Bile salts||Fat||Fat droplets|
|Pancreas||Small intestine||amylase protease lipase||Starch protein fat||Maltose amino acids glycerol and fatty acids|
|Small intestine||Small intestine||Maltose protein||Maltose protein||Glucose amino acids|
Mechanism of Enzyme Action :
→ Enzymes increase the rate of reaction without itself undergoing any change in the reaction. They gives a platform or template on which molecules react. Enzymes decrease the activation energy as a result of which rate of reaction increases at low temperatures.
→ Mechanism of enzyme action was given by Michaelis and Menten in 1913. According to this, an intermediate Enzyme-Substrate complex is formed. The mechanism of enzyme takes place in the following steps :
Step 1 : Formation of complex by reaction of substrate and enzyme.
E + S → [ES]
Step 2 : Conversion of this complex in an intermediate complex
[ES] → [ET]
Step 3 : In this step, intermediate complex is converted to enzyme product complex
[El] → [EP]
Step 5 : Conversion of product complex into enzyme and product
[EP] → E+P
Every enzyme has active centre.
Key-Lock structure of enzymes.
Application of Enzymes :
- Enzymes are mainly helpful in digestion.
- Enzyme renin is used commercial production of cheese.
- Enzymes like invertase, zymase and maltase are used manufacturing of alcoholic drinks.
- Some enzymes are used as therapeutic agents. For e.g., sreptokìnase is used to dissolve blood clots. Asparginase is used treatment of leukaemia.
- Enzymes are also used in treatment of diseases. For example, enzyme streptokinase is used in treatment of heart diseases. It is used in dissolution of blood clots.
Hormones are complex carbon compounds released by glands and cells which are responsible for control on various biochemical reactions, growth and development, reproduction of living beings. These are also known as glandular juices because they are secreted by endocrine glands. These are chemical messengers because they work in the cells and tissues away from their origin.
Very less quantity of hormones is more effective. These are destroyed after their action and are ejected by body through excretion.
Functions of Hormones :
→ Plant Hormones : These hormones are found in plants and helpful in growth of plants, formation of bud. Cell division, germination of seeds, formation of fruits, prevention of falling of unripened fruits and leaves and control of various living processes in plants.
→ Animal Hormones: In animals, hormones are secreted by endocrine glands and transported to target organ by blood. These control and coordinate various chemical reactions, growth, development, reproduction etc. in human beings.
→ Their deficiency and excess quantity both are harmful.
Enzymes vs Hormones :
Hormones also acts as catalyst like enzymes. These are used in very less amount and are not utilised during reaction. Though hormones are different from enzymes in the following properties:
- These acts on glands or organs which are different from their origin organs or gland.
- Structurally, they are not always proteins. These can be proteins of 30,000 or less molecular weight, small polypetide, single amino acids and steroids.
- These are released into the blood before use.
Classification of Hormones :
Hormones can be classified on the basis of their chemical constitution as:
→ Peptide Hormones : Peptide bond is found in these hormones. Therefore, these are known as peptide or protein hormones. Example is insulin, vasopressin and oxytocin.
→ Amino Hormones : These contain amino gioup and are soluble in water. Examples are adrenaline and thyroxin.
→ Steroid Hormones : These contain steroid nucleus. Steroid nucleus is made up of four rings. Three ring are of cyclohexane and one ring is of cyclopentane. Examples are sex hormones (like testosterone), adrenocorticol, cholesterol and bile acid etc.
Biological Fundions of Hormones :
Each hormone is released by a specific endocrine gland and perform a specific biological function. Following endocrine glands are found in human beings :
- Pituitary gland: One
- Thyroid gland: One
- Parathyroid gland: Four
- Adrenal gland : Two
- Islets of Langerhans
- Testes : Two (in males)
- Ovary (two in females)
- Placenta (one in females)
- Thymus gland (one)
- Pineal gland (one)
Biological functions of hormone is influenced by its structure. For example:
- Peptide hormone like vasopressiri etc. acts on peptide linkage.
- Iodine is present in thyroxine. Thus, it controls amount of iodine in the body.
- Similarly, cholesterol is a solid alcohol which is accumulated on the blood vessels and creates obstacle in blood flow.
Following table shows origin some of the important hormones and their functions:
Table: Important Hosmenc Functions
|Pituitary, anterior||ACTH, FSDH, Growth hormone, Prolaction, LH, TSH||Adrenal control, Gonad regulation, Growth Regulator ./mil k production, Milk production, Gonad regulation, thyroid control|
|Pituitary, posterior||ADH, Oxytocin||Water conservation, Uterus contraction and milk ejection|
|Thyroid||Thyroxine,||Metabolic rate control|
|Parathyroid||PTH, Calcitonin||Calcium regulation, Calcium regulation|
|Gut||Gut hormones||Food digestion|
|Pancreas||Insulin, Glucageon||Nutrient metabolism, Nutrient metaboilsm|
|Adrenals||Cortisol, Aldosterone, Epinephrine||Body preservation, Salt conservation Stress response|
|Ovaries||Estradiol, Progesterone||Female characteristics|