Side chain removal from corticosteroids by unspecific peroxygenase

René Ullrich,Marzena Poraj-Kobielska,Steffi Scholze,Claire Halbout,Martin Sandvoss,Marek J Pecyna,Katrin Scheibner,Martin Hofrichter

doi:10.1016/j.jinorgbio.2018.03.011

Abstract

Two unspecific peroxygenases (UPO, EC 1.11.2.1) from the basidiomycetous fungi Marasmius rotula and Marasmius wettsteinii oxidized steroids with hydroxyacetyl and hydroxyl functionalities at C17 - such as cortisone, Reichstein's substance S and prednisone - via stepwise oxygenation and final fission of the side chain. The sequential oxidation started with the hydroxylation of the terminal carbon (C21) leading to a stable geminal alcohol (e.g. cortisone 21-gem-diol) and proceeded via a second oxygenation resulting in the corresponding α-ketocarboxylic acid (e.g. cortisone 21-oic acid). The latter decomposed under formation of adrenosterone (4-androstene-3,11,17-trione) as well as formic acid and carbonic acid (that is in equilibrium with carbon dioxide); fission products comprising two carbon atoms such as glycolic acid or glyoxylic acid were not detected. Protein models based on the crystal structure data of MroUPO (Marasmius rotula unspecific peroxygenase) revealed that the bulky cortisone molecule suitably fits into the enzyme's access channel, which enables the heme iron to come in close contact to the carbons (C21, C20) of the steroidal side chain. ICP-MS analysis of purified MroUPO confirmed the presence of magnesium supposedly stabilizing the porphyrin ring system.

Highlights

The genus Marasmius contains about 500 species of agarics, most of which develop tiny inconspicuous fruiting bodies in leaf-litter or on coarse woody debris
M. wettsteinii is a member of the subsection Marasmius and related to M. bulliardii (Quél.) and M. rotula
Our isolated strain (DSM 106021) produced appreciable peroxygenase (UPO) activities with a maximum of 2,500 U L-1 in an N- and C-rich complex medium [2], which represents an about 15-times lower level compared to M. rotula but is in the same range as the activities observed for the UPOmodel fungus Agrocybe aegerita [3] (Fig. S1)

Summary

Introduction

The genus Marasmius contains about 500 species of agarics, most of which develop tiny inconspicuous fruiting bodies (mushrooms) in leaf-litter or on coarse woody debris. M. wettsteinii is a member of the subsection Marasmius and related to M. bulliardii (Quél.) and M. rotula. Antonin and Noordeloos described meticulously the differences of the basidiomata (M. wettsteinii ‘has, when fresh a white to cream colored pileus that becomes brownish or beige on drying’) and the ecology.

Results

Conclusion