Concerted action of the cytosolic sulfotransferase, SULT1A3, and catechol-O-methyltransferase in the metabolism of dopamine in SK-N-MC human neuroblastoma cells.
Conjugation reactions catalyzed by the cytosolic sulfotransferase, SULT1A3, or catechol-O-methyltransferase (COMT) are known to be involved in the regulation and homeostasis of dopamine and other monoamine neurotransmitters. Whether different conjugation reactions may act in a concerted manner, however, remains unclear. The current study aimed to investigate the concerted action of SULT1A3 and COMT in dopamine metabolism. Analysis of the medium of SK-N-MC cells, metabolically labeled with [(35)S]sulfate in the presence of dopamine, revealed the generation and release of predominantly [(35)S]sulfated 3-methyldopamine and, to a lesser extent [(35)S]sulfated dopamine. Addition to the labeling medium of tropolone, a COMT inhibitor, enhanced the production of [(35)S]sulfated dopamine, with a concomitant decrease of [(35)S]sulfated 3-methyldopamine. Enzymatic assays using the eleven known human cytosolic SULTs revealed SULT1A3 as the major enzyme responsible for the sulfation of both dopamine and 3-methyldopamine. Kinetic analysis showed that the catalytic efficiency of SULT1A3 with 3-methyldopamine was 1.6 times than that with dopamine. Using subcellular fractions prepared from SK-N-MC cells, the majority of COMT dopamine-methylating activity was found to be present in the cytosol. Collectively, these results imply a concerted action of sulfation and methylation in the irreversible inactivation and disposal of excess dopamine in SK-N-MC cells.
Yasuda
Shin
S
Department of Pharmacology, College of Pharmacy, The University of Toledo, Toledo, OH 43606, USA.
Yasuda
Tomoko
T
Hui
Ying
Y
Liu
Ming-Yih
MY
Suiko
Masahito
M
Sakakibara
Yoichi
Y
Liu
Ming-Cheh
MC
D015239:Arylsulfotransferase; D002394:Catechol O-Methyltransferase / Q000378:metabolism*; D065098:Catechol O-Methyltransferase Inhibitors; D002460:Cell Line; D003600:Cytosol / Q000201:enzymology; D003846:Deoxyepinephrine / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D007553:Isotope Labeling; D008745:Methylation / Q000187:drug effects; D009474:Neurons / Q000201:enzymology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D013379:Substrate Specificity; D013431:Sulfates / Q000378:metabolism; D015238:Sulfotransferases / Q000378:metabolism*; D014334:Tropolone / Q000494:pharmacology
D065098:Catechol O-Methyltransferase Inhibitors; D013431:Sulfates; D014334:Tropolone; D002394:Catechol O-Methyltransferase; D015238:Sulfotransferases; D015239:Arylsulfotransferase; C403170:monoamine-sulfating phenol sulfotransferase; D003846:Deoxyepinephrine; D004298:Dopamine