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Design of inhibitors for two oxygen-requiring metalloenzymes in steroid biosynthesis

Design of inhibitors for two oxygen-requiring metalloenzymes in steroid biosynthesis
Design of inhibitors for two oxygen-requiring metalloenzymes in steroid biosynthesis

A series of compounds was synthesised with a view to the inhibition of the enzyme Δ7-sterol-5(6)-desaturase (which is involved in the biosynthesis of membrane steroids such as cholesterol). Fifteen compounds were synthesised; these were sterols substituted with groups containing oxygen, nitrogen or sulphur at carbon atoms 5 and/or 6 of the steroid nucleus. An assay was developed for this enzyme, and each compound was tested for inhibition of 5-desaturase activity. The most effective inhibitors were those which contained a group with a single heteroatom forming a three-membered ring involving both C5 and C6.

A similar series of compounds was assayed for inhibition of the enzyme 17α-hydroxylase-17,20-lyase (also known as P-45017α or CYP17, and involved in the biosynthesis of androgen hormones are corticosteroid hormones). Fifteen compounds were tested, all of which were based upon the pregnane and androstane skeletons; most were substituted at carbon atoms 17,20 or 21. Those compounds which showed the most potent inhibition were substituted with one, two or three fluorine atoms at C21, or with a diazirine or diaziridine replacing the ketone at C20 of pregnenolone. Other good inhibitors had a diazo group at C21 or an acetate group replacing C20 and C21. Eight of these inhibitors were further characterised to determine their kinetic constant of inhibition Ki, using steady-state kinetics. Furthermore, the binding of seven of the inhibitors to P-45017α was analysed by measurement of the haem difference spectrum when the inhibitor was titrated with the enzyme.

Interestingly, the compounds with one and two fluorine atoms at C21 were also substrates for P-45017α, and it was shown that the products of the enzyme-catalysed reactions are the same as for the natural substrate, pregnenolone.

University of Southampton
Depledge, Nigel William
Depledge, Nigel William

Depledge, Nigel William (1997) Design of inhibitors for two oxygen-requiring metalloenzymes in steroid biosynthesis. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

A series of compounds was synthesised with a view to the inhibition of the enzyme Δ7-sterol-5(6)-desaturase (which is involved in the biosynthesis of membrane steroids such as cholesterol). Fifteen compounds were synthesised; these were sterols substituted with groups containing oxygen, nitrogen or sulphur at carbon atoms 5 and/or 6 of the steroid nucleus. An assay was developed for this enzyme, and each compound was tested for inhibition of 5-desaturase activity. The most effective inhibitors were those which contained a group with a single heteroatom forming a three-membered ring involving both C5 and C6.

A similar series of compounds was assayed for inhibition of the enzyme 17α-hydroxylase-17,20-lyase (also known as P-45017α or CYP17, and involved in the biosynthesis of androgen hormones are corticosteroid hormones). Fifteen compounds were tested, all of which were based upon the pregnane and androstane skeletons; most were substituted at carbon atoms 17,20 or 21. Those compounds which showed the most potent inhibition were substituted with one, two or three fluorine atoms at C21, or with a diazirine or diaziridine replacing the ketone at C20 of pregnenolone. Other good inhibitors had a diazo group at C21 or an acetate group replacing C20 and C21. Eight of these inhibitors were further characterised to determine their kinetic constant of inhibition Ki, using steady-state kinetics. Furthermore, the binding of seven of the inhibitors to P-45017α was analysed by measurement of the haem difference spectrum when the inhibitor was titrated with the enzyme.

Interestingly, the compounds with one and two fluorine atoms at C21 were also substrates for P-45017α, and it was shown that the products of the enzyme-catalysed reactions are the same as for the natural substrate, pregnenolone.

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Published date: 1997

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Local EPrints ID: 460261
URI: http://eprints.soton.ac.uk/id/eprint/460261
PURE UUID: 7a4470e5-cb06-48d5-91d8-17237c26e449

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Date deposited: 04 Jul 2022 18:17
Last modified: 04 Jul 2022 18:17

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Author: Nigel William Depledge

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