Alkaline phosphatase, placental type also known as placental alkaline phosphatase (PLAP) is an allosteric
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
that in humans is encoded by the ''ALPP''
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
.
Gene
There are at least four distinct but related alkaline phosphatases: intestinal (
ALPI Alpi may refer to:
* ALPI, an enzyme
* Alpi, the Italian word for the Alps
* Alpı (disambiguation)
Alpı is a Turkic word that may refer to:
* Alpı, Kastamonu, a village in the district of Kastamonu, Kastamonu Province, Turkey
* Alpı, Ulus, ...
), placental (this enzyme), placental-like (
ALPPL2), and liver/bone/kidney (
ALPL
Alkaline phosphatase, tissue-nonspecific isozyme is an enzyme that in humans is encoded by the ''ALPL'' gene.
Function
There are at least four distinct but related alkaline phosphatases: intestinal, placental, placental-like, and liver/bone/k ...
) (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.
Function
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.
Clinical significance
PLAP is a tumor marker, especially in
seminoma
A seminoma is a germ cell tumor of the testicle or, more rarely, the mediastinum or other extra-gonadal locations. It is a malignant neoplasm and is one of the most treatable and curable cancers, with a survival rate above 95% if discovered in e ...
and
ovarian cancer
Ovarian cancer is a cancerous tumor of an ovary. It may originate from the ovary itself or more commonly from communicating nearby structures such as fallopian tubes or the inner lining of the abdomen. The ovary is made up of three different ...
(e.g.,
dysgerminoma
A dysgerminoma is a type of germ cell tumor; it usually is malignant and usually occurs in the ovary.
A tumor of the identical histology but not occurring in the ovary may be described by an alternate name: seminoma in the testis or germinoma ...
).
PLAP is reliable only in non-smokers, as smoking interferes with measurement of PLAP,
since serum concentrations of PLAP are increased up to 10-fold in smokers and its measurement is therefore of little value in this group.
References
Further reading
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