Isozymes

Isoenzymes, also called as isozymes are the different forms of enzymes or group of enzymes that catalyze the same reaction but differ in their amino acid sequence thereby having the different structure, regulatory properties, different kinetic parameters, such as KM. The isozymes are encoded by the genes arise from gene duplication or/and divergence.  The isoenzymes are the enzymes of different genetic origins.

A very common example of an isozyme is lactate dehydrogenase (LDH). Lactate dehydrogenase catalyzes the reversible conversion of pyruvate into lactate. It belongs to 2-hydroxy acid oxidoreductase family. In human beings, LDH is found in two genetically distinct polypeptide chains, A (or M for muscle type) and B (or H for heart type), which form varying combinations of tetrameric structures to give five types of isozymes. These enzymes (isozymes) can be distinguished from each other based on their electrophoretic mobility by the process of electrophoresis.

There are five different forms of LDH: LDH-1, LDH-2, LDH-3, LDH-4, and LDH-5.

Type
Composition
Location
Eelectrophoretic mobility
LDH-1
H4
Mostly found in red blood cells and heart muscle
Fastest moving
LDH-2
H3M
In associated with the system in the body that defends against infection.
LDH-3
H2M2
Highly concentrated in the lungs
LDH-4
HM3
Highly concentrated kidney, placenta, and pancreas.
LDH-5
M4
In the liver and skeletal muscle.
Slowest moving

External links:

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Questions:

Isozymes

  1. What are Isozymes?
  2. What are the five isoenzymes of LDH?
  3. What parameters helps in the differentiation of Isoenzymes?
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