Sulphation of L-tyrosine in mammalian cells: a comparative study.
Chang liver cells, Caco-2 human intestinal epithelial cells and Madin-Darby canine kidney (MDCK) cells, labelled with [35S]sulphate in the presence of different concentrations of cycloheximide, produced 87.7-95.3%, 35.8-41.1% and 23.2-25.9%, respectively, of the amounts of free tyrosine O-[35S]-sulphate (Tyr[35S]) formed by corresponding cells labelled in the absence of cycloheximide. Homogenates prepared from the three kinds of cells showed the presence of enzymic activities catalysing the sulphation of L-tyrosine, with specific activities in the order: Caco-2 cells > MDCK cells > Chang liver cells. In all three cases, most of the tyrosine sulphotransferase' activity was found in the cytosolic fraction, indicating the enzyme to be a cysolic protein. A tyrosine-dependence experiment revealed that, for all three kinds of cells labelled with [35S]sulphate, the production of free Tyr[35S] was proportional to the concentration of L-tyrosine present in the culture medium. These results imply an involvement of sulphation in removing excess intracellular L-tyrosine.
Department of Biochemistry, University of Texas Health Center at Tyler 75710.
Y
Y
Sakakibara
M
M
Suiko
H
H
Nakajima
M C
MC
Liu
D000818:Animals; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004285:Dogs; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism*; D015238:Sulfotransferases / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*
D013431:Sulfates; D014443:Tyrosine; D003513:Cycloheximide; D015238:Sulfotransferases