Alkaline phosphatase (English: Alkaline phosphatase, referred to as ALP or ALKP) (EC 3.1.3.1) is a type of hydrolase that can remove phosphate groups from molecules such as nucleotides, proteins, and alkaloids for dephosphorylation The chemical reaction is most effective in an alkaline environment, hence the name alkaline phosphatase.
Bacterial alkaline phosphatase
In Gram-negative bacteria, alkaline phosphatase is located in the periplasmic space outside the cell membrane. Because the periplasmic space is more affected by environmental changes than the interior of the cell, bacterial alkaline phosphatase is less susceptible to inactivation, denaturation, and degradation and can maintain high activity. It is not completely clear why alkaline phosphatase is distributed here. A simple explanation is that alkaline phosphatase cleaves free phosphate here for absorption. Evidence supporting this idea is that alkaline phosphatase is normally synthesized when bacteria face a phosphate deficiency. However, there are other possibilities. For example, the presence of phosphate groups usually prevents biological macromolecules from permeating the cell membrane, while dephosphorylation may help bacteria absorb substances from the environment.
The optimal pH of Escherichia coli alkaline phosphatase is 8.0, while the optimal pH of domestic cattle is a little higher, reaching 8.5.
Human alkaline phosphatase
Physiological functions
In the human body, alkaline phosphatase is present in almost all tissues throughout the body, especially concentrated in the liver, bile ducts, kidneys, bones and placenta.
The following three alkaline phosphatase isoenzymes are found in the genomes of humans and other mammals:
ALPI – Intestinal (molecular weight 150 MDa)
Photoinitiator ALPL – Rohm and Haas resin; not tissue specific (liver, bone, kidney)
ALPP – Placenta
Application
For diagnosis
Under normal circumstances, the ALP level in adults is 20 to 140IU/L, and the levels in children and pregnant women are higher.
Levels increased
Level reduction
Indicates the possibility of hypophosphatasia
White blood cells
Application in scientific research
The most common application of alkaline phosphatase in the laboratory is to remove the phosphate group at the 5′ end of DNA to prevent self-linking of the vector.
