- Regioselective sulfonation of dopamine by SULT1A3 in vitro provides a molecular explanation for the preponderance of dopamine-3-O-sulfate in human blood circulation
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SULT1A3 is an enzyme that catalyzes the sulfonation of many endogenous and exogenous phenols and catechols. The most important endogenous substrate is dopamine (DA), which is often used as a probe substrate for SULT1A3. We developed a new method for analyzing the SULT1A3 reaction products by high-performance liquid chromatography (HPLC) with electrochemical detection. The sulfonate donor 3′-phosphoadenosine-5′-phosphosulfate (PAPS), DA and the two dopamine sulfates, DA-3-O-sulfate and DA-4-O-sulfate, can be separated within 3 min. This enables quantitation of the sulfates without radioactive PAPS or the precipitation of unreacted PAPS. Both sulfates were synthesized as reference substances and characterized by 1H and 13C nuclear magnetic resonance (NMR), mass spectrometry (MS) and tandem mass spectrometry (MS/MS). The purity of the dopamine sulfates was estimated by HPLC using a diode array detector. We determined the enzyme kinetic parameters for formation of DA-3-O-sulfate and DA-4-O-sulfate using purified recombinant human SULT1A3. The reactions followed Michaelis-Menten kinetics up to 50 μM DA concentration, and strong substrate inhibition was observed at higher concentrations. The apparent Km values for sulfonation at both hydroxy groups were similar (2.21 ± 0.764 and 2.59 ± 1.06 μM for DA-4-O-sulfate and DA-3-O-sulfate, respectively), but the Vmax was approximately six times higher for the formation of the 3-O-sulfate (344 ± 139 nmol/min/mg protein) than the 4-O-sulfate (45.4 ± 16.5 nmol/min/mg protein). These results are in accordance with the observation that DA-3-O-sulfate is more abundant in human blood than DA-4-O-sulfate and that in the crystal structure of SULT1A3 with dopamine bound to the active site, the 3-hydroxy group is aligned to form hydrogen bonds with catalytic residues of the enzyme.
- Itaeaho, Katriina,Alakurtti, Sami,Yli-Kauhaluoma, Jari,Taskinen, Jyrki,Coughtrie, Michael W.H.,Kostiainen, Risto
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- Fluorinated Phosphoadenosine 5′-Phosphosulfate Analogues for Continuous Sulfotransferase Activity Monitoring and Inhibitor Screening by 19F NMR Spectroscopy
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Sulfotransferases (STs) are ubiquitous enzymes that participate in a vast number of biological processes involving sulfuryl group (SO3) transfer. 3′-phosphoadenosine 5′-phosphosulfate (PAPS) is the universal ST cofactor, serving as the active sulfate source in cells. Herein, we report the synthesis of three fluorinated PAPS analogues that bear fluorine or trifluoromethyl substituents at the C2 or C8 positions of adenine and their evaluation as substitute cofactors that enable ST activity to be quantified and real-time-monitored by fluorine-19 nuclear magnetic resonance (19F NMR) spectroscopy. Using plant AtSOT18 and human SULT1A3 as two model enzymes, we reveal that the fluorinated PAPS analogues show complementary properties with regard to recognition by enzymes and the working 19F NMR pH range and are attractive versatile tools for studying STs. Finally, we developed an 19F NMR assay for screening potential inhibitors against SULT1A3, thereby highlighting the possible use of fluorinated PAPS analogues for the discovery of drugs for ST-related diseases.
- Mlynarska-Cieslak, Agnieszka,Chrominski, Mikolaj,Spiewla, Tomasz,Baranowski, Marek R.,Bednarczyk, Marcelina,Jemielity, Jacek,Kowalska, Joanna
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p. 661 - 669
(2022/03/15)
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- Synthesis and chemical properties of ibopamine and of related esters of N-substituted dopamines - Synthesis of ibopamine metabolites
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The therapeutic usefulness of intravenously infused dopamine in congestive heart failure and in shock prompted us to synthesize a wide series of 3,4-O-diesters of dopamine and N-substituted derivatives to obtain an orally active dopamine-like prodrug having adequate absorption and duration of action. The pharmacological results and in particular, the hemodynamic studies in the dog led to the selection of ibopamine, i.e. the 3,4-diisobutyryl ester of N-methyldopamine and to its development as a useful drug for the chronic treatment of congestive heart failure. The choice of ibopamine from among several analogs was also influenced by other favourable properties such as good chemical stability in pharmaceutical formulations and in the biopharmaceutical phases of the absorption, and fast enzymatic activation of the prodrug by plasma and peripheral tissue esterases; the latter property appeared desirable to avoid any accumulation in the central nervous system and consequent undesired side effects. The isomeric mixture of 3-O- and 4-O- isobutyrates of N-methyldopamine as well as the main conjugated metabolites, i.e. the 3-O- and 4-O-sulphate and 4-O-β-glucuronide of N-methyldopamine were synthesized as analytical references in metabolic studies and for the investigation of their pharmacokinetic and pharmacological properties. Dopamine O-sulphates were also prepared using the methods developed for the corresponding N-methyl derivatives.
- Casagrande,Santangelo,Saini,Doggi,Gerli,Cerri
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p. 291 - 303
(2007/10/02)
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