DESCRIPTION

Alkaline phosphatase (ALP) (EC 3.1.3.1)
catalyzes the hydrolysis of phosphate esters
in an alkaline environment, resulting in the
formation of an organic radical and inorganic
phosphate.
 Optimum pH of alkaline phosphatase activity
is 9-10
Orthophosphoric monoester + H2O → alcohol + H3PO4
Enzyme Secretion Sites
In humans, alkaline phosphatase is present
in all tissues throughout the entire body, but
is particularly concentrated in liver,
intestine, bone, and the placenta.
Diagnostic use
The normal range at 37 °C is
 Men (U/l) 80-302
 Women (U/l) 64-302
Physiological Increase:
 Growing children and pregnant women.
Pathological Increase:

Marked increase in serum ALP levels,, has been associated
with biliary obstruction (liver origin).
 Also, elevated ALP indicates that there could be active bone
deposition occurring as ALP is a by product of osteoblast
activity
such
as
the
case
in
rickets
and
hyperparathyrodism (bone origin).
Some examples of the signs and symptoms suggesting
a liver involvement may include:
 Weakness, fatigue
 Loss of appetite
 Nausea, vomiting
 Abdominal swelling and/or pain
 Jaundice
 Dark urine, light colored stool
 Itching (pruritus)
Some examples of the signs and symptoms suggesting
a bone disorder include:
 Bone and/or joint pain
 Increased frequency of fractures
 Deformed bones
Alkaline Phosphatase Assay
 The Alkaline Phosphatase Assay method utilizes pnitrophenyl phosphate that is hydrolyzed by ALP into a
yellow colored product (maximal absorbance at 405nm) at
37°C.
 The rate of the reaction is directly proportional to the
enzyme activity.
p-Nitrophenyl phosphate
ALP
p-nitrophenol +phosphate
(yellow)
Why Get Tested?
To screen for or monitor treatment for a liver or bone disorder.
Sample Required?
Serum or heparinised plasma.
Common Questions
1. What other tests are used to evaluate liver disorders?
Other commonly used liver tests include more enzymes
found in liver cells, such as alanine aminotransferase (ALT)
and aspartate aminotransferase (AST).
A test for bilirubin, a substance produced by the breakdown
of red blood cells and removed from the body by the liver,
may also be done.
Sometimes these tests are performed together as a liver
panel.
2. What other laboratory tests may be done if I have a
bone disorder?
Depending on the cause, your condition may be diagnosed
and/or monitored using other tests such as calcium,
phosphorus, vitamin D, or bone markers.