medical biochemistry

2. Enzymes as
Diagnostic tools

3. How?
*The measurement of the serum levels of
numerous enzymes has been shown to be
of diagnostic significance.
*This is because the presence of these
enzymes in the serum indicates that tissue
or cellular damage has occurred resulting
in the release of intracellular components
into the blood &this increases the level of
certain enzymes in blood according to the
damaged organ
What are the enzymes most used in
the diagnosis of certain diseases?

4. Plasma enzymes
Functional Non functional
**For example:-
1-Lactate dehydrogenase(LDH)
2-Creatine kinase(CK)
Izoenzymes
3-Alanine transminase(ALT) 4-Aspartate transminase(AST)
5-Alkaline phsphatase 6-Acid phosphatase
7-Amylase & Lipase enzymes

6. Lactate dehydrogenase(LDH)
Lactic acid Pyruvic acid
NAD NADH+H
*LDH is a tetramer(consists of 4 protomers)
*the protomers are 2 types:-
1-H(after heart)
2-M(after muscle)
so LDH have 5 isoenzymes:-

7. LDH 1 – Found in heart and red-blood cells and is 17% – 27% of the
normal serum total
*It is formed of HHHH.It increases in myocardial infarction
LDH 2 – Found in heart and red-blood cells and is 27% – 37% of the
normal serum total
*It is formed of HHHM.It increases in myocardial infarction
LDH 3 – Found in a variety of organs and is 18% – 25% of the normal
serum total
*It is formed of HHMM.It increases in leukaemia
LDH 4 – Found in a variety of organs and is 3% – 8% of the normal
serum total
*It is formed of HMMM.It increases in viral hepatitis
LDH 5 – Found in liver and skeletal muscle and is 0% – 5% of the
normal serum total
*It is formed of MMMM.It increases in viral hepatitis

9. Creatine kinase (CK)
Creatine Ceatine phosphate
ATP ADP
*CK is a dimmer (consists of 2 protomers)
*the protomers are 2 types:
1-B (after brain)
2-M (after muscle)
*so CK has 3 isoenzymes:-

10. .CPK1 (CPK-BB) is the characteristic isoenzyme in brain and is
in significant amounts in smooth muscle and is 0% of the normal
serum total.
**It increases in brain tumors.
.CPK2 (CPK-MB) accounts for about 35% of the CPK activity in
cardiac muscle , but less than 5% in skeletal muscle and is 0% of
the normal serum total.
**It increases in heart diseases.
.CPK3 (CPK-MM) is the predominant isoenzyme in muscle and
is 100% of the normal serum total.
**It increases in skeletal muscle diseases.

12. Alanine transminase(ALT)
*It is also called serum glutamic pyruvic transminase(SGPT)
*It catalyzes transfer of amino group (NH2) from
amino acid (alanine) to a-keto acid producting a new
amino acid & a new keto acid
*ALT is particularly diagnostic of liver involvement as this
enzyme is found predominantly in hepatocytes.
*It increases in liver & heart diseases.

13. Aspartate transminase(AST)
Glutamic oxalacetic
transminase(SGOT)
*It is also called aspartate glutamic oxalacetic
transminase(SGOT)
*It increases in liver & heart diseases
*When assaying for both ALT and AST the ratio of the level of these two
enzymes can also be diagnostic. Normally in liver disease or damage that is not
of viral origin the ratio of ALT/AST is less than1.with viral hepatitis the ALT/AST
ratio will be greater than1.
*The level of AST elevation in the serum is directly proportional to the number
of cells involved as well as on the time following injury that the AST assay was
performed. Following injury, levels of AST rise within 8 hours and peak 24–36
hours later. Within 3–7 days the level of AST should return to pre-injury levels
unless further injury occurs.
* Although measurement of AST is not, in and of itself, diagnostic for
myocardial infarction, taken together with LDH and CK measurements the level
of AST is useful for timing of the infarct

15. Alkaline phosphatase Acid phosphatase
**It is an enzyme which transport **is found in the prostate, red
phosphate groups across cell blood cells, small amounts
membranes of organs. are found in bone, liver,
**It is found in the spleen and pancreas.
osteoblasts,bile canali ,small
intestinal epithelium and **The assay of serum acid
proximal tubule. phosphatase is mostly used
**Increases mainly in bone to detect prostatic
diseases such as Osteogenic carcinoma and to monitor
sarcoma ,liver & bilary tract the treatment.
diseases and
hyperparathyroidism
**Amylase and lypase enzymes increases in diseases of the pancreas as
acute pancreatitis

17. Thank yo