The enzymatic basis for the rat liver 6-hydroxymelatonin sulfotransferase activity.
Understanding 6-hydroxymelatonin (6HM) sulfation is deemed important to explaining normal and oncostatic actions of the pineal gland. Here we identify the enzymatic basis for this sulfation in rats. First, a quantitative assay was designed for measuring hepatic 6HM sulfotransferase (6HMST) activity. The assay was then used to identify a male dominant sexual dimorphism wherein liver from males contains double the 6HMST per g or per 100 g body weight seen in females. Examination of other rat tissues showed that most in vivo 6HM sulfation was likely to occur in liver. In addition, DEAE-Sephadex chromatography of liver cytosol indicated that 80-90% of the 6HMST activity in both sexes was due to an enzyme we named 6HMST II. A minor 6HM sulfotransferase (6HMST I) eluted from the columns prior to the main enzyme. 6HMST II, purified additionally, was shown to convert 6HM to a product that appeared to be 6HM sulfate (6-sulfa-toxymelatonin). The enzyme was inhibited by Na+, K+, Zn2+, and Cd2+. Its pH optimum was 7.80 +/- 0.30. Comparisons are made between 6HMST II, dopamine sulfotransferase II, and aryl sulfotransferase IV.
Singer
S S
SS
Department of Chemistry, University of Dayton, Ohio 45469, USA.
Hagedorn
J E
JE
Smith
D M
DM
Williams
J L
JL
D000818:Animals; D015239:Arylsulfotransferase / Q000378:metabolism; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000201:enzymology; D004791:Enzyme Inhibitors; D004795:Enzyme Stability; D005260:Female; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology*; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D015238:Sulfotransferases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D004791:Enzyme Inhibitors; C094056:6-hydroxymelatonin sulfotransferase; D015238:Sulfotransferases; D015239:Arylsulfotransferase; D008550:Melatonin; C012365:6-hydroxymelatonin