Alkaline phosphatase, placental type also known as placental alkaline phosphatase (PLAP) is an allosteric enzyme that in humans is encoded by the ALPPgene.[5][6][7]
There are at least four distinct but related alkaline phosphatases: intestinal (ALPI), placental (this enzyme), placental-like (ALPPL2), and liver/bone/kidney (ALPL) (tissue-nonspecific). The first three are located together on chromosome 2, whereas the tissue-nonspecific form is located on chromosome 1. The coding sequence for this form of alkaline phosphatase is unique in that the 3' untranslated region contains multiple copies of an Alu family repeat. In addition, this gene is polymorphic and three common alleles (type 1, type 2, and type 3) for this form of alkaline phosphatase have been well-characterized.[7]
Alkaline phosphatase, placental type is a membrane-bound glycosylated dimeric enzyme, also referred to as the heat-stable form, that is expressed primarily in the placenta, although it is closely related to the intestinal form of the enzyme as well as to the placental-like form.[7]
PLAP is a tumor marker, especially in seminoma[8][9][10] and ovarian cancer (e.g., dysgerminoma).[11] PLAP is reliable only in non-smokers, as smoking interferes with measurement of PLAP,[12] since serum concentrations of PLAP are increased up to 10-fold in smokers and its measurement is therefore of little value in this group.[13]
^Fishman WH (December 1987). "Clinical and biological significance of an isozyme tumor marker--PLAP". Clin. Biochem. 20 (6): 387–92. doi:10.1016/0009-9120(87)90003-8. PMID3325192.
^Schmoll HJ, Souchon R, Krege S, et al. (September 2004). "European consensus on diagnosis and treatment of germ cell cancer: a report of the European Germ Cell Cancer Consensus Group (EGCCCG)". Annals of Oncology. 15 (9): 1377–99. doi:10.1093/annonc/mdh301. PMID15319245.
Knoll BJ, Rothblum KN, Longley M (1988). "Two gene duplication events in the evolution of the human heat-stable alkaline phosphatases". Gene. 60 (2–3): 267–76. doi:10.1016/0378-1119(87)90235-6. PMID3443302.
Ezra E, Blacher R, Udenfriend S (1984). "Purification and partial sequencing of human placental alkaline phosphatase". Biochem. Biophys. Res. Commun. 116 (3): 1076–83. doi:10.1016/S0006-291X(83)80252-6. PMID6651840.
Rump A, Kasper G, Hayes C, Wen G, Starke H, Liehr T, Lehmann R, Lagemann D, Rosenthal A (2001). "Complex arrangement of genes within a 220-kb region of double-duplicated DNA on human 2q37.1". Genomics. 73 (1): 50–5. doi:10.1006/geno.2000.6504. PMID11352565.
Wennberg C, Kozlenkov A, Di Mauro S, Fröhlander N, Beckman L, Hoylaerts MF, Millán JL (2002). "Structure, genomic DNA typing, and kinetic characterization of the D allozyme of placental alkaline phosphatase (PLAP/ALPP)". Hum. Mutat. 19 (3): 258–67. doi:10.1002/humu.10052. PMID11857742. S2CID44666573.
Tang J, Li W (2002). "[Methodological study on the assay of glycosylphosphatidylinositol-specific phospholipase D activity in serum]". Hunan Yi Ke da Xue Xue Bao. 24 (2): 119–22. PMID11938765.
Lehto MT, Sharom FJ (2002). "Proximity of the protein moiety of a GPI-anchored protein to the membrane surface: a FRET study". Biochemistry. 41 (26): 8368–76. doi:10.1021/bi012038+. PMID12081485.
Llinas P, Stura EA, Ménez A, Kiss Z, Stigbrand T, Millán JL, Le Du MH (July 2005). "Structural studies of human placental alkaline phosphatase in complex with functional ligands". J. Mol. Biol. 350 (3): 441–51. doi:10.1016/j.jmb.2005.04.068. PMID15946677.