Alkaline phosphatase

• CAS Number: 9001-78-9

Alkaline phosphatase (AP, ALP, knochenspez. Also Ostase ) is the name for enzymes that hydrolyze the phosphoric acid esters. Alkaline phosphatase to remove phosphate groups ( dephosphorylation ) of many types of molecules such as proteins, nucleotides, and alkaloids. They are most effective at an alkaline pH.

Alkaline phosphatases are found in almost all living creatures, except a few plants. An elevated laboratory value in humans may indicate a disease process, such as a biliary obstruction, internal organ damage, broken bones, a tumor or osteoporosis / osteomalacia ( rickets in children ).

Reaction

Alkaline phosphatase hydrolyzes phosphate esters to phosphate and alcohols, in which protons arise.

This enzyme works only in weakly alkaline solution. If you gave the enzyme to an unbuffered solution, the reaction came because of the proton release to a halt. In vitro they can therefore only be pursued in the presence of a buffer of suitable pH.

The human enzyme

In humans, 15 different isozymes are distinguished. Four of these isoenzymes derived from different genes ( small intestinal AP, placental AP, germ cell AP and tissue - nonspecific AP). The tissue - nonspecific AP are glycosylated differently depending on the tissue, that is, receives different sugar chains. This further isoenzymes ( liver AP, bone AP, kidney -AP).

Laboratory diagnostics

All of these enzymes is measured as the " alkaline phosphatase " in standard blood tests and can provide an indication of disease of the liver and present the skeleton.

The placental isoform ( PLAP ) is normally produced by placental syncytiotrophoblast. Your determination is recommended for seminomas. The half-life in blood serum is less than 3 days.

Reference range

For measurements at 37 ° C IFCC:

Infants 110-590 IU / l

Infants 110-550 IU / l

Schoolchildren 130-700 IU / l

Women 55-147 IU / l

Men 62-176 IU / l

Interpretation

Alkaline phosphatases are present in large amounts in the skeletal system, the liver parenchyma and the bile duct. Excessively high values ​​can cause their example, in diseases of the liver, gall bladder, thyroid or pancreas have. Also for bone diseases such as osteomalacia, Paget's disease, rickets, bone metastases, hyperparathyroidism, or in fractures, the value of AP is generally increased. One of the most common causes of AP increase are malignant tumors that have metastasized to the bone ( bone metastases).

Basically, both growing children and women in the last trimester of pregnancy have higher AP values ​​; However, this is normal and does not provide a fundamental indication of a disease.

A too low content of alkaline phosphatase found, eg, in the rare hereditary disease hypophosphatasia; In addition, as a side effect of a vitamin C deficiency ( scurvy ), as a result of bypass surgery, thyroid gland (hypothyroidism ), Wilson's disease, zinc deficiency, severe anemia, magnesium deficiency and oral contraceptive use.

In CML resulted in decreased alkaline phosphatase values ​​are found in the granulocytes.

Application in Biology

In biochemistry the alkaline phosphatase ( dyes ) are used in conjunction with a chromogenic substrate for various methods of detection:

• Antibody staining the Western blot for the detection of proteins
• The Northern blot and Southern blot for the detection of RNA or DNA
• In the in situ hybridization for the detection of RNA

Here, as a chromogenic substrate BCIP is often used in conjunction with NBT, which is converted from the alkaline phosphatase to a blue indigo dye.

In molecular biology, the Alkaline Phosphatase from calf intestine ( Calf Intestine Alkaline Phosphatase ) and shrimp (shrimp alkaline phosphatase) is used for dephosphorylation of linear DNA.

The most common alkaline phosphatases are:

• Bacterial alkaline phosphatase ( BAP), from Escherichia coli
• Calf Intestine Alkaline Phosphatase ( CIAP ), calf intestinal
• Shrimp Alkaline Phosphatase ( SAP), from the Arctic Sea shrimp ( Pandalus borealis)