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200  structures 1898  species 1  interaction 3561  sequences 33  architectures

Family: Alk_phosphatase (PF00245)

Summary: Alkaline phosphatase

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Alkaline phosphatase Edit Wikipedia article

Alkaline phosphatase
1ALK.png
Ribbon diagram (rainbow-color, N-terminus = blue, C-terminus = red) of the dimeric structure of bacterial alkaline phosphatase.[1]
Identifiers
EC number 3.1.3.1
CAS number 9001-78-9
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO
Alkaline phosphatase
PDB 1alk EBI.jpg
Structure of alkaline phosphatase.[1]
Identifiers
Symbol Alk_phosphatase
Pfam PF00245
InterPro IPR001952
SMART SM00098
PROSITE PDOC00113
SCOP 1alk
SUPERFAMILY 1alk

Alkaline phosphatase (ALP, ALKP) (EC 3.1.3.1) is a hydrolase enzyme responsible for removing phosphate groups from many types of molecules, including nucleotides, proteins, and alkaloids. The process of removing the phosphate group is called dephosphorylation. As the name suggests, alkaline phosphatases are most effective in an alkaline environment. It is sometimes used synonymously as basic phosphatase.[2]

Bacterial[edit]

In Gram-negative bacteria, alkaline phosphatase is located in the periplasmic space, external to the cell membrane. Since this space is much more subject to environmental variation than the actual interior of the cell, bacterial alkaline phosphatase is comparatively resistant to inactivation, denaturation, and degradation, and also has a higher rate of activity. Although the purpose of the enzyme is not fully resolved, the simple hypothesis that it is a means for the bacteria to generate free phosphate groups for uptake and use is supported by the fact that alkaline phosphatase is usually produced by the bacteria only during phosphate starvation and not when phosphate is plentiful.[3] However, other possibilities exist. For instance, the presence of phosphate groups usually prevents organic molecules from passing through the membrane; therefore, dephosphorylating them may be important for bacterial uptake of organic compounds in the wild.[4] Some complexities of bacterial regulation and metabolism suggest that other, more subtle, purposes for the enzyme may also play a role for the cell. In the laboratory, however, mutant Escherichia coli lacking alkaline phosphatase survive quite well, as do mutants unable to shut off alkaline phosphatase production.[5]

The optimal pH for the activity of the E. coli enzyme is 8.0[6] while the bovine enzyme optimum pH is slightly higher at 8.5.[7]

Use in research[edit]

Typical use in the lab for alkaline phosphatases includes removing phosphate monoester to prevent self-ligation.[8]

Common alkaline phosphatases used in research include:

  • Shrimp alkaline phosphatase (SAP), from a species of Arctic shrimp (Pandalus borealis). This phosphatase is easily inactivated by heat, a useful feature in some applications.
  • Calf-intestinal alkaline phosphatase (CIP)
  • Placental alkaline phosphatase (PALP) and its C terminally truncated version that lacks the last 24 amino acids (constituting the domain that targets for GPI membrane anchoring) - the secreted alkaline phosphatase (SEAP)

Alkaline phosphatase has become a useful tool in molecular biology laboratories, since DNA normally possesses phosphate groups on the 5' end. Removing these phosphates prevents the DNA from ligating (the 5' end attaching to the 3' end), thereby keeping DNA molecules linear until the next step of the process for which they are being prepared; also, removal of the phosphate groups allows radiolabeling (replacement by radioactive phosphate groups) in order to measure the presence of the labeled DNA through further steps in the process or experiment. For these purposes, the alkaline phosphatase from shrimp is the most useful, as it is the easiest to inactivate once it has done its job.

Another important use of alkaline phosphatase is as a label for enzyme immunoassays.

Undifferentiated pluripotent stem cells have elevated levels of alkaline phosphatase on their cell membrane, therefore alkaline phosphatase staining is used to detect these cells and to test pluripotency (i.e., embryonic stem cells or embryonal carcinoma cells).[9]

One common use in the dairy industry is as a marker of pasteurisation in cows' milk. This molecule is denatured by elevated temperatures found during pasteurisation, and can be tested for via colour change of a para-Nitrophenylphosphate substrate in a buffered solution (Aschaffenburg Mullen Test).[10] Raw milk would typically produce a yellow colouration within a couple of minutes, whereas properly pasteurised milk should show no change. Of course, there are exceptions to this, as in the case of heat-stable alkaline phophatases produced by some bacteria.

Inhibitors[edit]

All mammalian alkaline phosphatase isoenzymes except placental (PALP and SEAP) are inhibited by homoarginine, and, in similar manner, all except the intestinal and placental ones are blocked by levamisole. Heating for ~2 hours at 65°C inactivated most isoenzymes except Placental isoforms (PALP and SEAP).[11]

Human[edit]

Physiology[edit]

In humans, alkaline phosphatase is present in all tissues throughout the entire body, but is particularly concentrated in liver, bile duct, kidney, bone, and the placenta. Humans and most other mammals contain the following alkaline phosphatase isozymes:

  • ALPI – intestinal
  • ALPL – tissue-nonspecific (liver/bone/kidney)
  • ALPP – placental (Regan isozyme)

Diagnostic use[edit]

Normal ALP levels in adults are approximately 20 to 140 IU/L,[12] though levels are significantly higher in children and pregnant women. Blood tests should always be interpreted using the reference range from the laboratory that performed the test. High ALP levels can occur if the bile ducts are obstructed.[13] Also, ALP increases if there is active bone formation occurring, as ALP is a byproduct of osteoblast activity (such as the case in Paget's disease of bone). Levels are also elevated in people with untreated Coeliac Disease.[14] Lowered levels of ALP are less common than elevated levels.

Elevated levels[edit]

If it is unclear why alkaline phosphatase is elevated, isoenzyme studies using electrophoresis can confirm the source of the ALP. Heat stability also distinguishes bone and liver isoenzymes ("bone burns, liver lasts"). Placental alkaline phosphatase is elevated in seminomas[15] and active form of Rickets.

Lowered levels[edit]

The following conditions or diseases may lead to reduced levels of alkaline phosphatase:

In addition, the following drugs have been demonstrated to reduce alkaline phosphatase:

  • Oral contraceptives[16]

Leukocyte alkaline phosphatase[edit]

Leukocyte alkaline phosphatase (LAP) is found within white blood cells. White blood cell levels of LAP can help in the diagnosis of certain conditions.

See also[edit]

References[edit]

  1. ^ a b PDB 1ALK: Kim EE, Wyckoff HW (March 1991). "Reaction mechanism of alkaline phosphatase based on crystal structures. Two-metal ion catalysis". J. Mol. Biol. 218 (2): 449–64. doi:10.1016/0022-2836(91)90724-K. PMID 2010919. 
  2. ^ Tamás L, Huttová J, Mistrk I, Kogan G (2002). "Effect of Carboxymethyl Chitin-Glucan on the Activity of Some Hydrolytic Enzymes in Maize Plants". Chem. Pap. 56 (5): 326–329. 
  3. ^ Horiuchi T, Horiuchi S, Mizuno D (May 1959). "A possible negative feedback phenomenon controlling formation of alkaline phosphomonoesterase in Escherichia coli". Nature 183 (4674): 1529–30. doi:10.1038/1831529b0. PMID 13666805. 
  4. ^ Ammerman JW, Azam F (March 1985). "Bacterial 5-nucleotidase in aquatic ecosystems: a novel mechanism of phosphorus regeneration". Science 227 (4692): 1338–40. doi:10.1126/science.227.4692.1338. PMID 17793769. 
  5. ^ Wanner BL, Latterell P (October 1980). "Mutants affected in alkaline phosphatase, expression: evidence for multiple positive regulators of the phosphate regulon in Escherichia coli". Genetics 96 (2): 353–66. PMC 1214304. PMID 7021308. 
  6. ^ Garen A, Levinthal C (March 1960). "A fine-structure genetic and chemical study of the enzyme alkaline phosphatase of E. coli. I. Purification and characterization of alkaline phosphatase". Biochim. Biophys. Acta 38: 470–83. doi:10.1016/0006-3002(60)91282-8. PMID 13826559. 
  7. ^ Harada M, Udagawa N, Fukasawa K, Hiraoka BY, Mogi M (February 1986). "Inorganic pyrophosphatase activity of purified bovine pulp alkaline phosphatase at physiological pH". J. Dent. Res. 65 (2): 125–7. doi:10.1177/00220345860650020601. PMID 3003174. 
  8. ^ Maxam AM, Gilbert W (1980). "Sequencing end-labeled DNA with base-specific chemical cleavages". Meth. Enzymol. Methods in Enzymology 65 (1): 499–560. doi:10.1016/S0076-6879(80)65059-9. ISBN 978-0-12-181965-1. PMID 6246368. 
  9. ^ "Appendix E: Stem Cell Markers". Stem Cell Information. National Institutes of Health, U.S. Department of Health and Human Services. Retrieved 2013-09-24. 
  10. ^ Aschaffenburg R, Mullen JEC (1949). "A rapid and simple phosphatase test for milk". Journal of Dairy Research 16 (1): 58–67. doi:10.1017/S0022029900005288. 
  11. ^ Alkaline Phosphatase Why It Is Done from Everday Health.com. Retrieved October 15, 2012.
  12. ^ "MedlinePlus Medical Encyclopedia: ALP isoenzyme test". 
  13. ^ ALP: The Test
  14. ^ Preussner, Harold T, HT (March 1998). "Detecting coeliac disease in your patients". American Family Physician 57 (5): 1023–1034. PMID 9518950. 
  15. ^ Lange PH, Millan JL, Stigbrand T, Vessella RL, Ruoslahti E, Fishman WH (August 1982). "Placental alkaline phosphatase as a tumor marker for seminoma". Cancer Res. 42 (8): 3244–7. PMID 7093962. 
  16. ^ Schiele F, Vincent-Viry M, Fournier B, Starck M, Siest G (November 1998). "Biological effects of eleven combined oral contraceptives on serum triglycerides, gamma-glutamyltransferase, alkaline phosphatase, bilirubin and other biochemical variables". Clin. Chem. Lab. Med. 36 (11): 871–8. doi:10.1515/CCLM.1998.153. PMID 9877094. 
  17. ^ Arceci RJ, Hann IM, Smith OP, ed. (2006). Pediatric hematology (3rd ed.). Wiley-Blackwell. p. 763. ISBN 978-1-4051-3400-2. 

External links[edit]

Further reading[edit]

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This tab holds annotation information from the InterPro database.

InterPro entry IPR001952

This entry represents alkaline phosphatases (EC) (ALP), which act as non-specific phosphomonoesterases to hydrolyse phosphate esters, optimally at high pH. The reaction mechanism involves the attack of a serine alkoxide on a phosphorus of the substrate to form a transient covalent enzyme-phosphate complex, followed by the hydrolysis of the serine phosphate. Alkaline phosphatases are found in all kingdoms of life, with the exception of some plants. Alkaline phosphatases are metalloenzymes that exist as a dimer, each monomer binding metal ions. The metal ions they carry can differ, although zinc and magnesium are the most common. For example, Escherichia coli alkaline phosphatase (encoded by phoA) requires the presence of two zinc ions bound at the M1 and M2 metal sites, and one magnesium ion bound at the M3 site [PUBMED:15938627]. However, alkaline phosphatases from Thermotoga maritima and Bacillus subtilis require cobalt for maximal activity [PUBMED:11910033].

In mammals, there are four alkaline phosphatase isozymes: placental, placental-like (germ cell), intestinal and tissue-nonspecific (liver/bone/kidney). All four isozymes are anchored to the outer surface of the plasma membrane by a covalently attached glycosylphosphatidylinositol (GPI) anchor [PUBMED:17520090]. Human alkaline phosphatases have four metal binding sites: two for zinc, one for magnesium, and one for calcium ion. Placental alkaline phosphatase (ALPP or PLAP) is highly polymorphic, with at least three common alleles [PUBMED:11124260]. Its activity is down-regulated by a number of effectors such as l-phenylalanine, 5'-AMP, and by p-nitrophenyl-phosphonate (PNPPate) [PUBMED:15946677]. The placental-like isozyme (ALPPL or PLAP-like) is elevated in germ cell tumours. The intestinal isozyme (ALPI or IAP) has the ability to detoxify lipopolysaccharide and prevent bacterial invasion across the gut mucosal barrier [PUBMED:18292227]. The tissue-nonspecific isozyme (ALPL) is, and may play a role in skeletal mineralisation. Defects in ALPL are a cause of hypophosphatasia, including infantile-type (OMIM:241500), childhood-type (OMIM:241510) and adult-type (OMIM:146300). Hhypophosphatasia is an inherited metabolic bone disease characterised by defective skeletal mineralisation [PUBMED:17719863].

This entry also contains the related enzyme streptomycin-6-phosphate phosphatase (EC) (encoded by strK) from Streptomyces species. This enzyme is involved in the synthesis of the antibiotic streptomycin, specifically cleaving both streptomycin-6-phosphate and, more slowly, streptomycin-3-phosphate [PUBMED:1654502].

Gene Ontology

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Domain organisation

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Pfam Clan

This family is a member of clan Alk_phosphatase (CL0088), which contains the following 9 members:

Alk_phosphatase DUF1501 DUF229 Metalloenzyme PglZ Phosphodiest Phosphoesterase Sulfatase Sulfatase_C

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(10)
Full
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Representative proteomes NCBI
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Meta
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RP15
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RP35
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RP55
(845)
RP75
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  Seed
(10)
Full
(3561)
Representative proteomes NCBI
(2985)
Meta
(602)
RP15
(299)
RP35
(560)
RP55
(845)
RP75
(1070)
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Seed source: Prosite
Previous IDs: alk_phosphatase;
Type: Domain
Author: Finn RD
Number in seed: 10
Number in full: 3561
Average length of the domain: 329.70 aa
Average identity of full alignment: 28 %
Average coverage of the sequence by the domain: 81.45 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 19.8 19.8
Trusted cut-off 19.8 19.9
Noise cut-off 19.7 19.7
Model length: 421
Family (HMM) version: 15
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Interactions

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Alk_phosphatase

Structures

For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Alk_phosphatase domain has been found. There are 200 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.

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