Xylosyltransferase 2 is an
enzyme
An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
that in humans is encoded by the ''XYLT2''
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
Function
The protein encoded by this gene is an isoform of xylosyltransferase, which belongs to a family of
glycosyltransferases
Glycosyltransferases (GTFs, Gtfs) are enzymes ( EC 2.4) that establish natural glycosidic linkages. They catalyze the transfer of saccharide moieties from an activated nucleotide sugar (also known as the "glycosyl donor") to a nucleophilic glyc ...
. This enzyme transfers xylose from
UDP-
xylose
Xylose ( , , "wood") is a sugar first isolated from wood, and named for it. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group. It is deriv ...
to specific serine residues of the core protein and initiates the biosynthesis of
glycosaminoglycan
Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case o ...
chains in
proteoglycans
Proteoglycans are proteins that are heavily glycosylation, glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalent bond, covalently attached glycosaminoglycan (GAG) chain(s). The point of attachment is a ...
including
chondroitin sulfate
Chondroitin sulfate is a sulfated glycosaminoglycan (GAG) composed of a chain of alternating sugars (N-Acetylgalactosamine, N-acetylgalactosamine and glucuronic acid). It is usually found attached to proteins as part of a proteoglycan. A chondroit ...
,
heparan sulfate
Heparan sulfate (HS) is a linear polysaccharide found in all animal tissues. It occurs in a proteoglycan (HSPG, i.e. Heparan Sulfate ProteoGlycan) in which two or three HS chains are attached in close proximity to cell surface or extracellular ma ...
, heparin and
dermatan sulfate
Dermatan sulfate is a glycosaminoglycan (formerly called a mucopolysaccharide) found mostly in skin, but also in blood vessels, heart valves, tendons, and lungs.
It is also referred to as chondroitin sulfate B, although it is no longer classifi ...
.
Clinical significance
The enzyme activity, which is increased in
scleroderma
Scleroderma is a group of autoimmune diseases that may result in changes to the skin, blood vessels, muscles, and internal organs. The disease can be either localized to the skin or involve other organs, as well. Symptoms may include areas ...
patients, is a diagnostic marker for the determination of sclerotic activity in systemic sclerosis.
Mutations in this gene have been shown to be the cause of the
spondylo-ocular syndrome.
It has also been implicated as cofactor in
pseudoxanthoma elasticum
Pseudoxanthoma elasticum (PXE) is a genetic disease that causes mineralization of elastic fibers in some tissues. The most common problems arise in the skin and eyes, and later in blood vessels in the form of premature atherosclerosis. PXE is cau ...
.
References
Further reading
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