Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human UDP-d-xylose:proteoglycan core protein beta-d-xylosyltransferase (EC 2.4.2.26, XT-I) initiates the biosynthesis of glycosaminoglycan chains in proteoglycans by transferring xylose from UDP-xylose to specific serine residues of the core protein. Based on the partial amino acid sequence of the purified enzyme from human JAR choriocarcinoma cell culture supernatant we isolated a cDNA encoding XT-I using the degenerate reverse transcriptase-polymerase chain reaction method. This enzyme, which is involved in chondroitin sulfate, heparan sulfate, heparin and dermatan sulfate biosynthesis, belongs to a novel family of glycosyltransferases with no homology to proteins known so far. 5' and 3'-RACE were performed to isolate a novel cDNA fragment of 3726 bp with a single open reading frame encoding at least 827 amino acid residues with a molecular mass of 91 kDa. The human XT-I gene was located on chromosome 16p13.1 using radiation hybrid mapping, and extracts from CHO-K1 cells transfected with the XT-I cDNA in an expression vector exhibited marked XT activity. A new 3608 bp cDNA fragment encoding a protein of 865 amino acid residues was also isolated by PCR using degenerate primers based on the amino acid sequence of human XT-I. The amino acid sequence of this XT-II isoform displayed 55% identity to the human XT-I. The XT-II gene was located on chromosome 17q21.3-17q22, and the exon/intron structure of the 15 kb gene was determined. RT-PCR analyses of XT-I and XT-II mRNA from various tissues confirmed that both XT-I and XT-II transcripts are ubiquitously expressed in the human tissues, although with different levels of transcription. Furthermore, the cDNAs encoding XT-I and XT-II from rat were cloned. The deduced amino acid sequences of rat xylosyltransferases displayed 94% identity to the corresponding human enzyme.
J Mol Biol 2000 Dec 08
PMID:Molecular cloning and expression of human UDP-d-Xylose:proteoglycan core protein beta-d-xylosyltransferase and its first isoform XT-II. 1109 77

Follicular fluid proteoglycans play an important role in human oocyte maturation, including the development of a fluid-filled compartment and maintenance of the hypocoagulative state of the follicular fluid. Human xylosyltransferase (EC 2.4.2.26, XT) is the key enzyme in the biosynthesis of glycosaminoglycan chains in proteoglycans and is secreted into body fluids together with large proteoglycans. We investigated the XT activities in human follicular fluid and granulosa-lutein cells from women undergoing IVF procedures. The mean XT activity was determined as 17.7 mU/l, which is 20-fold higher than in serum and the highest XT activity ever found in body fluids. Cultured human granulosa-lutein cells secreted large amounts of XT (14.52 micro U/10(6) cells), indicating that these cells are the main source of this enzyme in human follicular fluid. The XT from human follicular fluid was found to be associated with large chondroitin sulphate-containing proteoglycans. Furthermore, heparin was shown to bind strongly to the follicular fluid XT and to inhibit its enzyme activity. These findings indicate that XT may play a role in maintaining the haemostatic potential of the follicular fluid.
Mol Hum Reprod 2002 Dec
PMID:High xylosyltransferase activities in human follicular fluid and cultured granulosa-lutein cells. 1246 40

In a journey lasting 40 years from the first reports on its activity in the 1960s to its purification and the cloning of relevant complementary DNAs, peptide O-xylosyltransferase has finally arrived at the same point as many other enzymes. This enzyme, whose systematic name is UDP-alpha-D-xylose:proteoglycan core protein beta-D-xylosyltransferase (EC 2.4.2.26), catalyses the first step in the biosynthesis of chondroitin, dermatan and heparan sulphates in the endoplasmic reticulum and/or the cis-Golgi cisternae. Analyses of their primary structure show that peptide O-xylosyltransferases are members of glycosyltransferase family 14 and so are homologous to beta1,6- N-acetylglucosaminyltransferases involved in O-glycan and poly- N-acetyllactosamine branching. Furthermore, vertebrates appear to have two rather similar genes encoding xylosyltransferase I and xylosyltransferase II, but enzymatic activity was only detected for a recombinant form of the first isoform. On the other hand, Caenorhabditis and Drosophila have each only one peptide O-xylosyltransferase gene. In the worm sqv-6 mutant, a mutation of the xylosyltransferase gene is associated with defective vulval morphogenesis, indicative of the importance of the glycosaminoglycan chains of proteoglycans in animal development. There remain, however, open questions, for instance, on the enzyme's intracellular localisation and structure-function relationships.
Cell Mol Life Sci 2004 Apr
PMID:The never-ending story of peptide O-xylosyltransferase. 1509 4

The xylosyltransferases I and II (XT-I, XT-II, EC 2.4.2.26) catalyze the transfer of xylose from UDP-xylose to selected serine residues in the proteoglycan core protein, which is the initial and ratelimiting step in glycosaminoglycan biosynthesis. Both xylosyltransferases are Golgi-resident enzymes and transfer xylose to similar core proteins acceptors. XT-I and XT-II are differentially expressed in cell types and tissues, although the reason for the existence of two xylosyltransferase isoforms in all higher organisms remains elusive. Serum xylosyltransferase activity was found to be a biochemical marker for the assessment of disease activity in systemic sclerosis and for the diagnosis of fibrotic remodeling processes. Furthermore, sequence variations in the XT-I and XT-II coding genes were identified as risk factors for diabetic nephropathy, osteoarthritis or pseudoxanthoma elasticum. These findings point to the important role of the xylosyltransferases as disease modifiers in pathologies which are characterized by an altered proteoglycan metabolism. The present review discusses recent advances in mammalian xylosyltransferases and the impact of xylosyltransferases in proteoglycan-associated diseases.
Cell Mol Life Sci 2007 Jun
PMID:Human xylosyltransferases in health and disease. 1743 56