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 useThe normal range at 37 °C isMen (U/l) 80-302Women (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 p-

nitrophenyl 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 Questions1.  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.