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Renin Angiotensin Mechanism.

Factors affecting enzyme action.

 

Introduction:

  • Enzymes are biocatalysts and are organic in nature. 

  • All enzymes are proteins in nature (except Ribozymes)

Factors affecting enzyme action.

  • Many factors affect enzyme activity, they are as follows,

    1. Temperature.

    2. Enzyme Concentration.

    3. pH.

    4. Substrate concentration.

    5. Product concentration.

    6. Activators and Inhibitors.

    7. Water.

  1. Temperature:

  • An enzyme's activity is greatest within a narrow temperature range.

  • The temperature at which an enzyme exhibits maximum activity is referred to as the optimum temperature.

  • The optimum temperature for most of the enzymes is between 25-35°C.  Temperature above and below this range affects the enzyme activity. 

  • High temperature above 50°C results in the destruction of enzymes by causing their denaturation, and very low temperature restores the enzymes in their inactive state.

  1. Enzyme Concentration:

  • The rate of the enzymatic reaction increases with increasing enzyme concentration until it reaches a point known as the saturation point.

  • Above this limit, there is very little effect on enzyme activity.

  1. pH:

  • Enzymes work at their optimum pH. 

  • Increase or decrease in pH reduces the activity of enzymes. 

  • Most of the intracellular enzymes function near-neutral pH except for many digestive enzymes that are active in different pH ranges. 

  • Change in pH causes change in the structure of the enzyme, including its active site. 

  • At extreme pH, denaturation of enzymes occurs.

  1. Substrate concentration: 

  • At the start, the rate of enzymatic reaction increases with the increase in substrate concentration. 

  • In the beginning, the velocity of the reaction is high, but later it does not increase progressively with the increase in substrate concentration. 

  • It happens because enzyme molecules get fully saturated, and no more active sites are left free to bind additional substrates.

  • In the graph below, the low value of Km (Michaelis-Menten constant) indicates a strong affinity between the enzyme and substrate. 

  • On the other hand, a high value of Km shows a weak affinity between the enzyme and the substrate.

  1. Product concentration: 

  • The accumulation of the products of reaction causes decreases in the activity of enzymes. 

  • When products accumulate, they combine with the active site of enzymes, thus forming a loose complex that inhibits the activity of enzymes.

  1. Activators and Inhibitors: 

  • Some chemical substances or molecules increase the activity of enzymes such as cofactors, for example, manganese ion (Mn²⁺), etc.  

  • These chemicals which increase the activity of enzymes are known as activators. 

  • On the other hand, certain drugs or poisons inhibit the activity of enzymes e.g. heavy metal compounds, Allopurinol which is used in Gout.

  1. Water: 

  • Water is the place in which enzymatic reactions take place. 

  • The presence of water increases the reaction rate, whereas the absence of water inhibits the enzyme activity.

  1. Light: 

  • Enzymes are sensitive to light. 

  • The presence of light increases the reaction rate in some enzymes whereas the presence of harmful radiation such as UV rays and X-rays decomposes enzymes.

Commonly Asked Question.

  1. What are Enzymes? Discuss various factors affecting enzyme activity.
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