Factors affecting enzyme activity


what are the Factors affecting enzyme activity? what type of Factors affecting enzyme activity? uses of Factors affecting enzyme activity?

 Factors affecting enzyme activity:-

The contact between enzyme and substrate is the most essential for enzyme activity.

Concentration of enzymes:-

As the concentration of enzymes increases the velocity of the reaction proportionally increases.

Concentration of substrate:-

In the substrate concentration gradually increases the velocity of the enzyme reactions. A rectangular hyperbola is obtained when velocity is plotted against substrate concentration.

Allow  substrate concentration the velocity of reaction is directly proportional to substrate level.

In the second phase the substrate concentration is not directly proportional to the enzyme activity.

In the third was the reaction is independent of the substrate.

Concentration of substrate

Effect of temperature:-

Velocity of the enzyme reaction increases at the temperature up to a maximum and then decline. A bell shaped curve is usually obtained.

The optimum temperature for the most of the year 42-450 except muscle adenylate kinase activate at 1000c.

Effect of temperature on enzymes

Effect of ph:-

It is a bell shaped curve, each enzyme has an optimum ph at which the velocity is maximum below and above the ph the enzyme activity is much lower and at extreme ph.

The enzyme ph becomes totally inactive.

Optimum activity is around ph 6to8 except pepsin.

H2n ions influence the enzyme activity altering the ionic charges in the amino acid.

Effect of ph on enzyme

Effect of the product of concentration:-

The accumulation of reaction products generally decreases the enzyme velocity.

The product combined with the active site of enzyme and forms a loose complex and thus inhibits enzyme activity.

Effect of activator:-

Some of the enzymes require certain inorganic metal cations like magnesium, calcium, potassium, for their optimum activity.

Rarely anions also needs  for enzymes activity.

{a} metal activated enzymes:-

The metal is tightly held by the enzyme and can be easily exchanged with the other ions.

{b}Metallo enzymes:-

These are the enzymes hold the metal tightly which are not readily exchange.

Example:- pyruvate oxidase.

Effect of time:-

Variation in the time of the reaction {or} generally related alternation in ph and temperature.

Effect of light and radiation:-

Expossed of enzymes to u.v rays, β-rays, x rays inactive certain enzymes due to the formation of peroxides.

When the uv rays exposed to salivary amalyase its activity deminished.

Enzyme kinetics:-

It is a study of the enzyme velocity of reactions catalysed by enzymes the units of velocity or ketal.

Michaels muten equation:-

  • This equation describes the dependence of reaction velocity on substrate concentration.
  • Michaels muten  proposed in any enzymatic reaction the enzyme combines with substrate to form an enzyme substrate complex.
  • The enzyme substrate complex can associate again to form and enzyme and substrate can produce chemical to form enzyme  and product.
Michaels muten equation on enzymes
Michaels muten equation on enzymes
  • The rates at which the reaction this model occur are described by the rate constant k1 k2 k3.
  • According to this model the increase in the initial velocity observed which an increase in substrate velocity concentration due to an increase in the amount of es formed.
  • At vmax all of the enzymes is involved in a complex.
Michaels muten equation on enzymes
Michaels muten equation
  • If k1 = substrate concentration then v0 = vmax/2.
  • Thus km  can be defined as [s] that produce 1/2max conc km is a constant characteristic for every enzymes and particular substrate km reflects the affinity of the enzyme for the substrate smaller km value more active enzyme [high affinity for the enzyme towards the substrate]
  • High km value reflects the low affinity  of the enzyme towards the substrate. 
Lineweaver burk plot

Lineweaver burk plot:-

  • Vmax is achieved alpha substrate concentration it is impossible to estimate v max and hence km forms a hyperbolic plot
  • Lineweaver burk plot of1/v0 against 1/s is made this plot is deviation of mechalis  menten equation which give the straight line which intercept on the x-axis equal to  1/v max and the intercept on the y-axis equal to 1 /km
  • The slope of the line is equal to km/vmax
  • The lineweaver burk plot is also determine is how on inhibitor binds to an enzyme

Enzyme inhibition:-

 Any substance that can reduce the velocity of an enzymatic reaction is called inhition

 Example:- foreign drugs and toxins

The inhibition of the enzyme can be classified as

1 reversible  2 irreversible

Irreversible inhibition:-

 Inhibitors which bind irreversibly to an enzyme often form a covalent bond to an amino acid residue at active sites and permanently inactive the enzyme suspectable amino acid residue includes serine  cystine respectively

The compound disaropryl phospho fluoridate [dfp] reacts with serine and residue in the active site of an enzyme. Acetyl choline esterase, irreversible inhibiting the enzyme and preventing the transmission of nerve impulse.

Irreversible inhibition

Competitive inhibition:-

Reversible competitive inhibitor:-

This type of inhibition occurs when the inhibitiors binds irreversibly to the active site where the substrate normally would occupy.

Therefore both inhibitor and substrate complete for active site. Here is the structural similarly between substrate and inhibitor. The enzymes may bind either substrate molecule {or} an inhibitor molecule but not both at the same time.

At high substrate concentration the action of a competitive inhibitor is overcome because of a sufficiently high concentration will successfully out of the inhibitor molecule in binding to the active site.

Thus there is no change in the vmax of the enzyme but the apparent affinity of the enzyme for its substrate decreases in the presence of the competitive inhibitor and hence km increases.

Line weavers burk plot showing the affect of a competitive inhibitor or km and vmax.

Leave a comment