Effects of ATP on regulation of galactosyltransferase-I activity responsible for synthesis of the linkage region between the core protein and glycosaminoglycan chains of proteoglycans.
We report that ATP enhances the activity of galactosyltransferase-I, which synthesizes the linkage region between glycosaminoglycan chains and the core proteins of proteoglycans. The enzyme activity in cell-free fractions prepared from cultured human skin fibroblasts was measured by high-performance liquid chromatographic detection of galactosyl-xylosyl-(4-methylumbelliferone) produced from 4-methylumbelliferyl-beta-D-xyloside used as an acceptor. ATP at 2 mM increased the enzyme activity by about 60% in the 110 x g supernatant of the cell homogenate, but not in the supernatant or precipitate fractions obtained by 100,000 x g centrifugation. When both fractions (the 100,000 x g supernatant and precipitate) were mixed, the additional ATP increased the enzyme activity. This increase was canceled by heat treatment or trypsin digestion of the 100,000 x g supernatant. In addition, the 100,000 x g precipitate, which was prepared from the 110 x g supernatant preincubated with ATP, exhibited increased activity, and this increase was abolished by alkaline phosphatase treatment. These results suggest that a protein kinase in the 100,000 x g supernatant activates galactosyltransferase-I activity.
Higuchi
T
T
Department of Biochemistry, Hirosaki University School of Medicine, Japan.
Tamura
S
S
Tanaka
K
K
Takagaki
K
K
Saito
Y
Y
Endo
M
M
D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000328:Adult; D000469:Alkaline Phosphatase / Q000378:metabolism* / Q000494:pharmacology; D002458:Cell Fractionation; D002478:Cells, Cultured; D002874:Chromosome Mapping; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005347:Fibroblasts / Q000201:enzymology; D005700:Galactosyltransferases / Q000187:drug effects / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000737:chemistry / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D006923:Hymecromone / Q000031:analogs & derivatives / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism / Q000494:pharmacology; D011509:Proteoglycans / Q000737:chemistry / Q000378:metabolism*; D012867:Skin / Q000166:cytology; D014357:Trypsin / Q000378:metabolism* / Q000494:pharmacology; D014758:Viral Core Proteins / Q000378:metabolism*
D006025:Glycosaminoglycans; D011509:Proteoglycans; D014758:Viral Core Proteins; D006923:Hymecromone; C014111:methylumbelliferyl-beta-D-xyloside; D000255:Adenosine Triphosphate; D005700:Galactosyltransferases; C063053:xylosylprotein 4-beta-galactosyltransferase; D011494:Protein Kinases; D000469:Alkaline Phosphatase; D014357:Trypsin