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. Author manuscript; available in PMC: 2018 Nov 1.
Published in final edited form as: Biochim Biophys Acta. 2017 Aug 3;1861(11 Pt A):2883–2890. doi: 10.1016/j.bbagen.2017.08.005

Figure 6. Proposed sulfation mechanism for steroids in the active site of hSULT2A1.

Figure 6

(A) Conventional enzymatic mechanism of SULT-mediated sulfation of DHEA [29]. (B) Proposed mechanism for the sulfation of ketosteroid by SULT2A1. In this model, the highly conserved His99 and W77 may collaboratively act to deprotonate the C-6 proton of 4-androstene-3,17-dione to form a enolate intermediate. The resulting nucleophilic oxyanion then attacks the sulfur of PAPS via a SN2 reaction, followed by the production and release of sulfated 4-androstene-3,17-dione from the active site.