Δ 4 -3-ketosteroids as a new class of substrates for the cytosolic sulfotransferases

Abstract

Cytosolic sulfotransferase (SULT)-mediated sulfation is generally known to involve the transfer of a sulfonate group from the active sulfate, 3’-phosphoadenosine 5’-phosphosulfate (PAPS), to a hydroxyl group or an amino group of a substrate compound. We report here that human SULT2A1, in addition to being able to sulfate dehydroepiandrosterone (DHEA) and other hydroxysteroids, could also catalyze the sulfation of Δ4-3-ketosteroids, which carry no hydroxyl groups in their chemical structure. Among a panel of Δ4-3-ketosteroids tested as substrates, 4-androstene-3,17-dione and progesterone were found to be sulfated by SULT2A1. Mass spectrometry analysis and structural modeling supported a reaction mechanism which involves the isomerization of Δ4-3-ketosteroids from the keto form to an enol form, prior to being subjected to sulfation. Results derived from this study suggested a potential role of SULT2A1 as a Δ4-3-ketosteroid sulfotransferase in steroid metabolism.

A new type of sulfation reaction: C-sulfonation for α,β-unsaturated carbonyl groups by a novel sulfotransferase SULT7A1

“…While the reaction mechanism for the sulfonation of α,β-unsaturated carbonyl groups by hSULT1C4 is still unresolved, a key point of the novel sulfonation may be the generation of a nucleophilic atom capable of attacking the sulfur atom of PAPS. Interestingly, in the O -sulfonation of ketosteroids, it is proposed that SULT2A1 deprotonates the C-6 proton of ketosteroids though the catalytic residue His, forms an enolate intermediate, and generates a nucleophilic oxyanion which attacks the sulfur atom of PAPS ( 15 ). The difference between O -sulfonation and C -sulfonation may be due to the stability of oxyanion, which is usually unstable.…”

“…Therefore, human SULT1C4 may be involved in the metabolism of other α,β-unsaturated carbonyl compounds, such as quinones. Additionally, our recent work showed that SULT2A1 is capable of catalyzing the O -sulfonation of ketosteroids in a manner distinct from that catalyzed by SULT7A1 ( 15 ). The proposed reaction mechanisms found for α,β-unsaturated carbonyl groups are different between O -sulfonation and C -ulfonation, implying that sulfonation of α,β-unsaturated carbonyl groups may be just one of the ways to generate a nucleophile attack at the sulfur atom of PAPS.…”

“…By confining to this widely accepted viewpoint, compounds that may undergo sulfonation at locations other than the hydroxy or amino group thus may be overlooked. Indeed, a recent study reported the O -sulfonation of ketosteroids, having neither hydroxy nor amino groups, by a hydroxysteroid SULT, SULT2A1 ( 15 ). The discovery of ketosteroid O -sulfonation clearly suggests that SULT enzymes may be capable of modifying not only hydroxy and amino groups but also carbonyl groups.…”

“…Therefore, metabolism of α,β-unsaturated carbonyl compounds plays an important role in regulation of the positive health effects and detoxification of the cytotoxic effects. α,β-Unsaturated carbonyl compounds are mainly metabolized through β-oxidation and glutathione conjugation ( 14 , 15 ). Although glutathione conjugation attenuates the reactivity and toxicity of α,β-unsaturated carbonyl compounds ( 14 ), an intensive glutathione conjugation reaction can lead to intracellular GSH depletion.…”

Progesterone: A Steroid with Wide Range of Effects in Physiology as Well as Human Medicine

“…The effects of pregnane steroids are summarized in Table 3. As with DHEAS and deoxycorticosterone, PROG and its derivatives are sulfated by SULT2A1 [105]. PROG itself is also an important regulator of SULT1E1 activity, which is responsible for estrogen sulfation [106].…”