Alanine transaminase or ALT
transaminase enzyme (EC 126.96.36.199).
It is also called serum glutamic pyruvic
ALT is found in serum and in various body
tissues, but is most commonly associated with
It is the reaction between an amino acid and an
alpha-keto acid. The amino group is transferred
from the former to the latter; this results in the
amino acid being converted to the corresponding
α-keto acid, while the reactant α-keto acid is
converted to the corresponding amino acid.
Transamination in biochemistry is accomplished
This process is an important step in the synthesis
of some non-essential amino acids (amino acids
that are not supplied from the diet).
is commonly measured clinically as a part
of a diagnostic liver function test, to
determine liver health.
Diagnostically, it is almost always measured
in units/liter (U/L).
Normal level in serum:
ALT < 45 units/ml
Viral or autoimmune hepatitis.
Lack of blood flow to the liver (liver ischemia).
Death of liver tissue (liver necrosis).
Use of drugs that are poisonous to the liver.
Biliary duct problems. For this reason, ALT is
commonly used as a way of screening for liver
When elevated ALT levels are found in the blood,
the possible underlying causes can be further narrowed
down by measuring other enzymes.
For example, elevated ALT levels due to liver-cell
damage can be distinguished from biliary duct problems
by measuring alkaline phosphatase.
ALT Activity Assay Principle
spectrophotometric assay uses enzymatic reaction:
L-Alanine + α-ketoglutaric acid
L-Glutamic acid + Pyruvic
Pyruvic acid + NADH
L-Lactic acid + NAD+
The absorbance is measured at 505 nm, is
proportional to the level of ALT enzyme in the
Why Get Tested?
To screen for liver damage and/or to help diagnose liver
When is it ordered?
To evaluate a person who has symptoms of a liver disorder:
Weakness, fatigue, Loss of appetite
Abdominal swelling and/or pain
Dark urine, light colored stool
What does the test result mean?
Very high levels of ALT (more than 10 times the
highest normal level) are usually due to acute
hepatitis, often due to a virus infection.
In acute hepatitis, ALT levels usually stay high
for about 1–2 months but can take as long as 3–
6 months to return to normal.
ALT levels are usually not as high in chronic
hepatitis, often less than 4 times the highest
causes of moderate increases in ALT
include obstruction of bile ducts, cirrhosis
and with tumors in the liver.
most types of liver diseases, the ALT
level is higher than AST.
are a few exceptions. The AST/ALT
ratio is usually increased in alcoholic
hepatitis, cirrhosis, and with muscle injury.
Aspartate transaminase (AST) also
called serum glutamic oxaloacetic
transaminase (SGOT) (EC 188.8.131.52) is
similar to alanine transaminase (ALT) in
that it is another enzyme associated with
liver parenchymal cells.
Aspartate Transaminase Isozymes
Two isoenzymes are present in humans.
GOT1, the cytosolic isoenzyme derives
mainly from red blood cells and heart.
GOT2, the mitochondrial isoenzyme is
predominantly present in liver.
AST <40 units/ml
It is raised in acute liver damage. It is also
present in red blood cells and cardiac muscle,
skeletal muscle and may be elevated due to
damage to those sources as well.
AST was defined as a biochemical marker for
the diagnosis of acute myocardial infarction
in 1954. However the use of AST for such a
diagnosis is now redundant and has been
superseded by the cardiac troponins.
AST (SGOT) is commonly measured clinically as
a part of diagnostic liver function tests, to
determine liver health.
Glutamic-Pyruvic Transaminase (GPT) is
found in significant quantities in liver,
kidney, and skeletal muscle, in decreasing
order. When liver cells are damaged, GOT
and GPT levels rise especially early in the
In hepatitis, transaminase levels rise several
days before jaundice begins. The enzyme
levels are especially useful in assessing
subtle and early changes in biliary
obstruction and active cirrhosis.
AST Activity Assay
L-Aspartate + α-ketoglutarate
L-Glutamate + Oxaloacetate
The oxaloacetate obtained is measured in its derative from
2,4 dinitropheny hydrazone.
The absorbance is measured at 505 nm, is proportional to
the level of ALT enzyme in the sample.
Transaminases (GOT and GPT)
Glutamic-Oxaloacetic Transaminase (GOT)
occurs in large concentrations in the heart
and liver with moderate amounts in skeletal
muscle, kidneys, and pancreas.
GOT levels can be used to diagnose
myocardial infarction within 10-48 hours.
Other conditions with elevated GOT include
arrhythmias and severe angina of the heart,
and liver damage.