LIVER ENZYMES AST, ALT & ALP

LIVER ENZYMES
AST, ALT & ALP

1. SUBMITTED TO:- DR. TARVEEN DHINDSA
SUBMITTED BY:- MOIN KHAN HUSSAIN
UID:-14BBT1129
CLINICAL BIO CHEMISTRY
PRESENTATIONc
M. Zaharna Clin. Chem. Lab. 2009

2. Lab. 5

3. Aminotransferases
•Aminotransferases or transaminases are a group of
enzymes that catalyze the interconversion of amino
acids and ketoacids (oxoacids) by transfer of amino
group
•The two aminotransferases of greatest clinical
significance are:
•Aspartate aminotransferase (AST), formerly termed
glutamate oxaloacetate transaminase (GOT).
•Alanine aminotransferase (ALT), formerly termed
glutamate pyruvate transaminase (GPT).
•Pyridoxal phosphate (P-5-P) is coenzyme

4. Aspartate aminotransferase (AST)
•AST involved in the transfer of an amino group between
aspartate and µ-ketoacids.

5. Specimen Collection & Storage
•Specimen:
•Serum, heparin plasma or EDTA plasma
•Hemolysis should be avoided because it can dramatically
increase serum AST concentrations
•(RBCs contain 15 X the AST activity in serum)
•Post AMI
•Rises 6 – 8 hours
•Peaks at 24 hours
•Returns to normal by day 5
•AST levels are highest in acute hepatocellular disorders "viral
hepatitis, cirrhosis.

6. Assay for Enzyme activity
•Measurement by Karmen method
•A coupled reaction involving:
•pyridoxal-5-phosphate (P-5-P)
•and malate dehydrogenase (MDH)
•at 37
o
C:
•Decrease in absorbance at 340 nm is determined by
continuous monitoring.
Aspartate + a-Ketoglutarate Oxaloacetate + Glutamate


Oxaloacetate + NADH + H Malate + NAD
MD
AST

7. Alanine Aminotransferase (ALT)
•A transferase with enzymatic activity similar to AST
•Converts alanine + α-ketoglutarate to pyruvate and glutamate

8. Assay for enzyme activity
•The most common method in use today for measurement of
ALT activity utilizes a coupled enzymatic procedure for
monitoring disappearance of NADH.
•In this approach lactate dehydrogenase (LDH) and its required
cofactors are added and catalyze the conversion of pyruvate to
lactate
•This causes simultaneous oxidation of reduced nicotinamide
adenine dinucleotide (NADH).
•The disappearance of NADH is followed spectrophotometrically
(at 340 nm).
Alanine + a-Ketoglutarate Pyruvate + Glutamate

Pyruvate + NADH + H Lactate + NAD
LD
ALT

9. Levels of AST & ALT
•AST is assessed along ALT in monitoring liver damage.
•These two values normally exist in an approximately 1:1 ratio.
•As a rough guide:
•AST>ALT in:
•alcoholic hepatitis and cirrhosis,
•metastatic cancer of the liver
•non-biliary cirrhosis,
•while ALT>AST in:
•viral and drug hepatitis,
•chronic hepatitis C
•and hepatic obstruction.

10. Alkaline Phosphatase (ALP)
•Phosphatases transfer a phosphate moiety from one group
to a second, forming an alcohol and a second phosphate
compound.
•The optimal reaction pH for ALP is between 9 and 10 and
varies with the buffer and substrate.
•ALP requires Mg
2+
as an activator

11. Isoenzymes
•ALP exists as a number of isoenzymes
•Major are those found in Liver, bone,
placenta, and then intestinal fraction
•Electrophoresis for isoenzyme analysis
•Liver isoenzyme (fastest)
•Bone isoenzyme
•Placental isoenzyme
•Intestinal isoenzyme (slowest)
•Immunochemical methods now available
Mohammed Laqqan

12. M. Zaharna Clin. Chem. Lab. 2009