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Electrocatalytic Hydroxylation of Sterols by Steroid C25 Dehydrogenase from Sterolibacterium denitrificans
Author(s) -
Kalimuthu Palraj,
Wojtkiewicz Agnieszka M.,
Szaleniec Maciej,
Bernhardt Paul V.
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201800616
Subject(s) - hydroxylation , chemistry , catalysis , substrate (aquarium) , dehydrogenase , electron transfer , medicinal chemistry , steroid , regioselectivity , electrochemistry , organic chemistry , enzyme , electrode , biochemistry , oceanography , geology , hormone
The electrochemically driven catalysis of the complex molybdoenzyme steroid C25 dehydrogenase (S25DH) from the β‐Proteobacterium Sterolibacterium denitrificans is reported. S25DH catalyses the oxygen‐independent regioselective hydroxylation of the tertiary C25 atom of sterols and also their derivatives. Cholest‐4‐en‐3‐one is a native substrate for S25DH, which produces 25‐hydroxycholest‐4‐en‐3‐one as a product of catalytic turnover. Cholecalciferol (vitD 3 ) is also a substrate. S25DH was immobilised on a modified gold working electrode with the co‐adsorbent chitosan. The complexes ferricyanide ([Fe(CN) 6 ] 3− ) and ferrocenium methanol (FM + ) are effective artificial electron acceptors from S25DH and act as mediators of electron transfer between the electrode and the enzyme. 2‐Hydroxypropyl‐β‐cyclodextrin (HPCD) was employed as a sterol solubiliser, in addition to 2‐methoxyethanol. The catalytic activity varied, depending upon the concentration of solubiliser in the reaction mixture. Parallel studies with [Fe(CN) 6 ] 3− as a chemical (as opposed to electrochemical) oxidant coupled to HPLC analysis show that S25DH is capable of oxidising both vitD 3 and its less stable isomer, pre‐vitD 3 , and that the former substrate is stabilised by HPCD.