Category: Biology Second Paper

Protease enzyme : Definition and activities

Enzymes that break down proteins into amino acids are called proteases. The process of breaking down proteins is called proteolysis. It is also called proteolytic or systemic enzyme. Protease enzymes digest protein-rich foods. For example, pepsin, trypsin, erepsin, papain etc. Uses or importance of protease are-
(i) Protease enzymes are used to improve bread quality.
(ii) It is used to control blood clotting.
(iii) It has uses in the preparation of medicines.
(iv) It breaks down animal carcasses and releases nitrogen and carbon into the environment.
(v) Protease enzymes are used in biological research.

Effectors of Enzyme

1. Temperature: Enzyme activity increases with increasing temperature, but is destroyed at higher temperatures. The best temperature for enzymes is 35-400C. 00C. Most enzymes are inactivated by heat. The temperature is 450C. Above this, the enzyme denatures or denatures.
2. Water: Enzymes are inactive in the absence of water. Increasing the amount of water increases the rate of enzyme action.
3. pH : Enzyme activity is controlled by pH. The optimum pH of enzymes is trypsin-8.0, urease-7.0, cellubiase-5.0, invertase-4.5, pepsin-2.0 etc.
4. Substrate concentration: Enzyme activity increases as substrate concentration increases and enzyme activity decreases as substrate concentration decreases.
5. Enzyme concentration: Increase in enzyme concentration increases the rate of reaction and decrease in enzyme concentration decreases the reaction.
6. Co-enzymes: Enzyme activity increases in the presence of any co-enzyme. Eg ATP, ADP, NAD, NADP, FAD, FADP etc.
7. Metals or metals: The presence of metals both increases and decreases enzyme activity. Enzyme activity increases in presence of Mg2+, Mn2+ etc.
8. Oxidation: Some enzymes are activated by oxidation and are inactivated by exposure to mild oxidizing agents. For example, sulfhydryl.
9. Inhibitors: The presence of substances that temporarily or permanently stop the action of enzymes are called inhibitors. High energy radiation, salts of heavy metals, cyanide, dinitrophenol, formalin etc. are inhibitors.
10. Activator: Activator activates the inactive enzyme. Inactive pepsinogen is converted to active pepsin under the influence of HCl. Like Cl+, Mg++, Ca++, Mn++ etc.
11. Contact: Enzyme and substrate come into contact with each other and form compounds. Enzyme action occurs when the compound is formed.
12. Irradiation: High energy radiation (α, β and γ rays) causes structural deviation of the enzyme and reduces the activity.
13. Inhibiting agents: Metals whose presence inhibits enzyme activity are called inhibitory agents. Like Ag, Zn, Hg, Cu etc.

Enzyme induction theory

In 1966 D. Koshland presented the hypothesis of enzyme mechanism of action. The obsession doctrine can also be called a modified version of the lock-and-key doctrine. In this theory, the structure of the enzyme is variable. Such enzymes are called allosteric. The obsessional doctrine is discussed as follows:
A special type of protein is an enzyme. The site of apoenzyme where the substrate binds and causes the reaction is called the active site or reaction center. Enzymes contain one or more active sites. The size of the substrate and the size of the enzyme’s active site can vary. According to induction theory, the substrate does not require a specific conformation or affinity to bind to the enzyme’s active site. Rather, the binding of the substrate molecule requires some modification of the active site of the enzyme. Such modification makes the active site fit for the substrate. As a result, the substrate binds to the active site of the enzyme. The enzyme assumes its maximal catalytic shape after binding to the substrate. The substrate and enzyme are then joined by hydrogen bonding to form an enzyme-substrate complex. Once the enzyme-substrate complex is formed, the enzyme readily cleaves the substrate. At the end of the reaction, the product is freed from the bond and moved away and the enzyme is released unchanged. The free enzyme takes part in the new reaction.
The obsession theory has gained acceptance among many scientists. In support of this model, X-ray observations of carboxypeptidase-A and several other enzymes are presented
[According to D.Koshland, the active site of an enzyme consists of two parts. buttracing groups and catalytic groups. The buttracing group holds the substrate and the catalytic group helps to weaken various substances in the substrate to reactants]

Mykilis and Menten Theory of Enzyme

In 1913, scientists Michael and Menten expressed the theory about the mechanism of action of enzymes called Michaelis-Menten theory. This doctrine is similar to the doctrine of lock and key. The doctrine is discussed.
An enzyme is a type of protein made up of numerous amino acids. The site of apoenzyme where the substrate binds and causes the reaction is called the active site. Each enzyme has one or more active sites or reaction centers. The substrate binds to the enzyme’s active site or reaction center to form an enzyme-substrate complex. Enzymes dissociate after product formation. The rate of enzyme reaction is related to the concentration of substrate. As the concentration of substrate increases, the rate of enzyme action increases. The Michaelis constant (Km) of the reaction is called the Michaelis constant (Km) of the reaction half the maximum speed due to increase in substrate concentration. The Michaelis constant is a special feature of enzymes. The rate of reaction is determined by the value of Km.

Lock and Key Theory of enzymes

In 1898, the German scientist Emil Fisher published the lock-key theory about the mechanism of action of enzymes. According to this theory, a specific enzyme binds to a specific substrate in a lock-and-key manner to form an enzyme-substrate complex, so named. The lock-key doctrine is discussed.
Enzymes are special types of proteins made up of numerous amino acids. Each enzyme molecule has a specific shape. The site of their apoenzyme where the substrate binds and causes the reaction is called the active site. Each enzyme has one or more active sites or reaction centers. The size of the substrate and the size of the enzyme’s active site are always the same. According to the lock-key theory, a specific substrate molecule or molecules are attached like a key to the active site or reaction center of a specific enzyme. This is called induced fit. The substrate molecule then joins with the enzyme molecule by hydrogen bonding to form the enzyme-substrate complex. A single substrate binds to an active site of an enzyme. More than one substrate can never bind to an active site. Just as a lock does not open without a specific key, a specific enzyme does not act on any substrate other than a specific substrate. When an enzyme-substrate complex is formed, the enzyme easily cleaves the substrate or bonds between the molecules to form larger molecules. At the end of the reaction, the product is freed from the bond and moved away and the enzyme is released intact. The free enzyme takes part in the new reaction.
According to the lock-key theory, the shape of the substrate molecule participating in the reaction must be suitable for joining the active site or reaction center of the enzyme. Even the slightest change in the size of the enzyme and substrate results in a change in activity.
Modern studies have revealed that some enzymes act on multiple substrates. Pepin enzyme is reactive on 60-180 substrate molecules. For this reason, many scientists question the lock-key theory.