3-Ketosteroid 9α-hydroxylase enzymes: Rieske non-heme monooxygenases essential for bacterial steroid degradation

Abstract

Various micro-organisms are able to use sterols/steroids as carbon- and energy sources for growth. 3-Ketosteroid 9α-hydroxylase (KSH), a two component Rieske non-heme monooxygenase comprised of the oxygenase KshA and the reductase KshB, is a key-enzyme in bacterial steroid degradation. It initiates opening of the steroid polycyclic ring structure. The enzyme has industrial relevance in the synthesis of pharmaceutical steroids. Deletion of KSH activity in sterol degrading bacteria results in blockage of steroid ring opening and is used to produce valuable C19-steroids such as 4-androstene-3,17-dione and 1,4-androstadiene-3,17-dione. Interestingly, KSH activity is essential for the pathogenicity of Mycobacterium tuberculosis. Detailed information about KSH thus is of medical relevance, and KSH inhibitory compounds may find application in combatting tuberculosis. In recent years, the 3D structure of the KshA protein of M. tuberculosis H37Rv has been elucidated and various studies report biochemical characteristics and possible physiological roles of KSH. The current knowledge is reviewed here and forms a solid basis for further studies on this highly interesting enzyme. Future work may result in the construction of KSH mutants capable of production of specific bioactive steroids. Furthermore, KSH provides an promising target for drugs against the pathogenic agent M. tuberculosis.

Molecular characterization of a new gene cluster for steroid degradation in Mycobacterium smegmatis

“…4-androstene-3,17-dione (AD), 1,4-androstadiene-3,17-dione (ADD) or 9a-hydroxy-4androstene-3,17-dione (9OH-AD). Thereafter, the catabolism of AD, ADD and 9OH-AD has been postulated to proceed for aerobic bacteria through a common catabolic route called 9,10-seco pathway involving two key activities D 1 -ketosteroid dehydrogenase (KSTD) and 3-ketosteroid 9a-hydroxylase (KSH) (van der Geize et al, 2001;Knol et al, 2008;Wei et al, 2010b;Fern andez de las Heras et al, 2012;Rohman et al, 2013;Petrusma et al, 2014;Yao et al, 2014). KSH is a two component class IA monooxygenase comprised of the terminal oxygenase KshA and the reductase component KshB (Andor et al, 2006;van der Geize et al, 2008;Petrusma et al, 2009;Capyk et al, 2009a,;Petrusma et al, 2011;Penfield et al, 2014) This enzyme introduces a 9a-hydroxyl group fundamental for steroid B-ring opening and thus, for its further degradation Petrusma et al, 2014).…”

Distinguishing Protonation States of Histidine Ligands to the Oxidized Rieske Iron–Sulfur Cluster through 15N Vibrational Frequency Shifts

“…[1] These include the CÀHa ctivation step in the biosynthesis of some antibiotics [3] and somes teroids. [4] The Rieske cluster in these enzymesi sp roposed to pass electrons to am ononuclear iron complext hat comprises the enzyme's catalytic core. [5] Structural studies [6] and measurements of pHdependentr edox potentials [7] imply protonation of one His ligand of the Rieske cluster upon its reduction (for possible protonation states of the two His ligands to the Rieske ironsulfur cluster,s ee the captiont oF igure 1).…”

Genome‐wide Transcriptional Analysis of Tetrahymena thermophila Response to Exogenous Cholesterol

“…; Petrusma et al. ). We were unable to identify orthologues of ferredoxin reductases but detected three putative ferredoxins (TTHERM_00161840, TTHERM_00256970, and TTHERM_00590010), although none of them appeared differentially regulated.…”