Human homolog of Caenorhabditis elegans sqv-3 gene is galactosyltransferase I involved in the biosynthesis of the glycosaminoglycan-protein linkage region of proteoglycans.
A cDNA encoding a novel galactosyltransferase was identified based on BLAST analysis of expressed sequence tags, and the cDNA clones were isolated from a human melanoma line library. The new cDNA sequence encoded a type II membrane protein with 327 amino acid sequence and showed 38% homology to the Caenorhabditis elegans sqv-3 gene involved in the vulval invagination and oocyte development. Extracts from L cells transfected with the galactosyltransferase cDNA in an expression vector and a fusion protein with protein A exhibited marked galactosyltransferase activity specific for p-nitrophenyl-beta-D-xylopyranoside. Moreover, transfection with the cloned cDNA restored glycosaminoglycan synthesis of galactosyltransferase I-deficient Chinese hamster ovary mutant pgsB-761 cells. Analysis of the enzyme product by beta-galactosidase digestion, mass spectroscopy, and NMR spectroscopy revealed that the reaction product was formed via beta-1,4 linkage, indicating that the enzyme is galactosyltransferase I (UDP-galactose:O-beta-D-xylosylprotein 4-beta-D-galactosyltransferase, EC 2.4.1.133) involved in the synthesis of the glycosaminoglycan-protein linkage region of proteoglycans.
Okajima
T
T
Department of Biochemistry II, Nagoya University School of Medicine, Tsurumai, Nagoya 466-0065, Japan.
Yoshida
K
K
Kondo
T
T
Furukawa
K
K
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary; D005700:Galactosyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006025:Glycosaminoglycans / Q000378:metabolism*; D016695:Glycosyltransferases / Q000235:genetics* / Q000378:metabolism; D015801:Helminth Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D011509:Proteoglycans / Q000096:biosynthesis* / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
D029742:Caenorhabditis elegans Proteins; D018076:DNA, Complementary; D006025:Glycosaminoglycans; D015801:Helminth Proteins; D011509:Proteoglycans; D016695:Glycosyltransferases; D005700:Galactosyltransferases; C117429:SQV-3 protein, C elegans; C063053:xylosylprotein 4-beta-galactosyltransferase