ISOENZYME INTRODUCTION HISTORY DEFINATION EXPLANATION FOR THE EXISTENCE OF ISOENZYME IMPORTANT EXAMPLE OF ISOENZYME LACTATE DEHYDROGENASE(LDH) CREATINE PHOSPHOKINASE(CPK) ALKALINE PHOSPHATASE (ALP) REFERENCE

1. ISOENZYME:TYPES AND
CLINICAL
SIGNIFICANCE
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. CONTENTS
ISOENZYME
 INTRODUCTION
 HISTORY
 DEFINATION
EXPLANATION FOR THE EXISTENCE OF
ISOENZYME
IMPORTANT EXAMPLE OF ISOENZYME
 LACTATE DEHYDROGENASE(LDH)
 CREATINE PHOSPHOKINASE(CPK)
 ALKALINE PHOSPHATASE (ALP)
 REFERENCE

3. INTRODUCTION
 Isoenzymes are enzymes that differ in amino acid
sequance but catalyses the same chemical reaction.
 They posses different kinetic properties(such as
isoelectric point,
pH optimum,substrate affinity
 They can be separated by appropriate techniques
such as eletrophoresis.
 Isoenzyme are homologous enzymes with in a
single organism.

4. HISTORY
 1st discover by R.L.Hunter and Clement Markert
(1957)
 D1efined as different variant of the same enzyme
having identical functions and present in the same
individual.
 Different isoenzyme forms of a given enzyme are
usually derived from different genes and often
occurs in different tissue of the body.

5. DEFINITION
 The multiple forms of an enzyme catalysing the
same reaction are isoenzymes or isozymes.
 They differ in their physical and chemical
properties which include the
structure,electrophoretic and immunological
properties,Km and Vmax values,pH optimum.

6. Explanation for the existence of isoenzyme
Many possible reason are offered to explain the
presence of isoenzymes in the living systems.
 Oligomeric enzymes consisting of more than one type of
subunit
e.g.-lactate dehydrogenase and creatine phosphokinase
 An enzyme may be active as monomer or oligomer
e.g.-Glutamate dehydrogenase.
 Glycoprotein enzymes,differences in carbohydrate content
may be responsible for isoenzyme
e.g.-Alkaline phosphatase

7. Value and significance of different
isoezymes
LACTATE DEHYDROGENASE OF
ISOENZYME
LDH catalyzes the reversible oxidation of
lactate to pyruvate.
CH3 LDH CH3
C=O CHOH
COOH COOH
PYRUVIC ACID NADH NAD LACTIC ACID
• +H
• LDH catalyses the interconversion of NADH and NAD
• LDH is an oxidoreductase enzyme.

8. LDH has five physically distinct
isoenzymes
 LDH-1,LDH-2,LDH-3,LDH-4,LDH-5
 An tetrameric enzyme madeup of four polypeptide
subunits. There are two type of subunit M(for muscle)
and H(for heart) are produced by different genes.
 The different forms can be separated by electrophoresis.
 Electrophoretic mobilities is due to different electric
charges on the isoenzymes due to difference in contents
of acidic and basic amino acids.

9. STRUCTURE OF LDH ISOENZYMES
Isoenzyme
Subunit
constitution
Principle tissue of
origin
Electrophoretic
mobility
Whether
distroyed
by heat
LDH-1
LDH-2
LDH-3
LDH-4
LDH-5
H4
H3M
H2M2
HM3
M4
Heart & RBC
Heart & RBC
Brain &Kidney
Liver & skeletal
muscle
Liver & skeletal
muscle
Fastest
Faster
Fast
Slow
Slowest
NO
NO
Partially
Yes
Yes
%normal
serum in
human
25%
35%
27%
8%
5%

10. DIFFERENTIATION OF ISOENZYME OF LDH
 Simpler chemical identification of these patterns by:
Heat stability
Inhibition with urea
Reaction with changed “Substrate”

11. CLINICAL SIGNIFICANCE
 Isoenzyme of LDH have immense value in the diagnosis
of HEART and LIVER related disorders.
o Damage of these tissues(Myocardium and Liver)
o Total serum LDH is increased
 In normal serum LDH-2(H3M) is most prominent.
 After myocardial infarction,the faster isoenzymes LDH-
1 and LDH-2 predominate.
 An accute viral hepatitis, the slowest isoenzymes LDH-5
and LDH-4 (HM3) prodominate

12. ISOEZYME OF CPK
 Creatine phosphokinase catalyses the interconversion
of phosphocreatine to creatine.
CPK
Phosphocreatine Creatine
ADP ATP
• In human tissues,CPK exists as three different
isoenzymes
• Each isoenzyme is a “dimer” composed of two
protomers ‘M’(for muscle) and ‘B’(for brain).

13. THREE ISOENZYME ARE
CPK ISOENZYME
Types Polypeptide Eletrophoretic Tissue found
chain mobility
CPK-1 BB fast moving Brain
(more –ve charge)
CPK-2 MB Heart
CPK-3 MM slow moving Skeletal
muscle

14. CLINICAL SIGNIFICANCE
 Myocardial infarction(Heart attack)
 Brain injury(bleeding in the brain or stroke)
 Pulmonary infarction
 Muscular dystrophy
 Skeletal muscle inflammation(Myositis)
 Normally CK(MB) very small (obout 2 % of total CK activity of
plasma)

15. ISOENZYME OF ALP
 ALP is monomer molecule
 ALP Is a hydrolase enzyme
 It is responsible for DEPHOSPHORYLATION
ALP present in all tissues, in human
But it is perticularly concentrated in LIVER, BONE,
INTESTINE and PLACENTA

16. MAJOR FOUR ISOENZYME
The major isoenzymes found in SERUM are derived
from liver, bone intestine and placenta.
Hepatic isoenzyme
Bone isoenzyme
Placental isoenzyme
Intestinal isoenzyme

17. CLINICAL SIGNIFICANCE
 The major liver band increased in many hepetobiliary
diseases and in metastetic carcinoma of liver.
 The two subsidiary bond form a “doublet” in
extrahepetic obstructive jaundice.
BONE ISOENZYME- increases due to osteoblastic
activity
 Normally elevated in children during period of growth
 In adults over the age of 50
IN PREGNANCY- placental isoenzyme of ALP
increased during last six weeks of pragnancy.

19. REFERENCE
Lehninger Principles Of Biochemistry, FIFTH edition,
David L. Nelson & Michael M. Cox.
Biochemistry, Fifth edition, Jeremy M. Berg, John L.
Tymoczko,Lubert Stryer.
W.H.Freeman and company
Biochemistry,Third edition, U. Satyanarayna &U.
Chakrapani
Medical Biochemistry, Third edition, Chatergee