Phosphatase Fold AP

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Phosphatase Classification: Fold AP

Alkaline phosphatase is a conserved phosphatase that has a broad of substrates, including proteins. It is used in clinical lab test, diary industry and biomedical research.


Alkaline phosphatases are found in metazoa, fungi, some protists, and bacteria, but are absent from most plants. They belong to the alkaline phosphatase-like fold (SCOP), which contains other enzymes, such as phosphoesterases and sulfatases.


Alkaline phosphatases are a superfamily (Pfam) with a wide variety of substrates, possibly including phosphoproteins. There are four human alkaline phosphatases, named by their tissue expression: ALPI (alkaline phosphatase, intestinal), ALPP (alkaline phosphatase, placental), ALPPL2 (alkaline phosphatase, placental-like 2), and ALPL (alkaline phosphatase, liver/bone/kidneytissue). Early reports found that ALPL and ALPI can dephosphorylate Histone H2A [1, 2] and that PLAP is a protein tyrosine phosphatase [3], but their physiological relevance as protein phosphatases is still unclear.


  1. Swarup G, Cohen S, and Garbers DL. Selective dephosphorylation of proteins containing phosphotyrosine by alkaline phosphatases. J Biol Chem. 1981 Aug 10;256(15):8197-201. PubMed ID:6167574 | HubMed [Swarup]
  2. Chan JR and Stinson RA. Dephosphorylation of phosphoproteins of human liver plasma membranes by endogenous and purified liver alkaline phosphatases. J Biol Chem. 1986 Jun 15;261(17):7635-9. PubMed ID:3011792 | HubMed [Chan]
  3. Telfer JF and Green CD. Placental alkaline phosphatase activity is inversely related to cell growth rate in HeLaS3 cervical cancer cells. FEBS Lett. 1993 Aug 30;329(3):238-44. PubMed ID:8396040 | HubMed [Telfer]
All Medline abstracts: PubMed | HubMed