Molecular Mechanism Study on Stereo-Selectivity of α or β Hydroxysteroid Dehydrogenases

Hydroxysteroid dehydrogenases (HSDHs) are from two superfamilies of short-chain dehydrogenase (SDR) and aldo–keto reductase (AKR). The HSDHs were summarized and classified according to their structural and functional differences. A typical pair of enzymes, 7α–hydroxysteroid dehydrogenase (7α–HSDH) and 7β–hydroxysteroid dehydrogenase (7β–HSDH), have been reported before. Molecular docking of 7-keto–lithocholic acid(7–KLA) to the binary of 7β–HSDH and nicotinamide adenine dinucleotide phosphate (NADP+) was realized via YASARA, and a possible binding model of 7β-HSDH and 7-KLA was obtained. The α side of 7–KLA towards NADP+ in 7β–HSDH, while the β side of 7–KLA towards nicotinamide adenine dinucleotide (NAD+) in 7α-HSDH, made the orientations of C7–OH different in products. The interaction between Ser193 and pyrophosphate of NAD(P)+ [Ser193–OG···3.11Å···O1N–PN] caused the upturning of PN–phosphate group, which formed a barrier with the side chain of His95 to make 7–KLA only able to bind to 7β–HSDH with α side towards nicotinamide of NADP+. A possible interaction of Tyr253 and C24 of 7–KLA may contribute to the formation of substrate binding orientation in 7β–HSDH. The results of sequence alignment showed the conservation of His95, Ser193, and Tyr253 in 7β–HSDHs, exhibiting a significant difference to 7α–HSDHs. The molecular docking of other two enzymes, 17β–HSDH from the SDR superfamily and 3(17)α–HSDH from the AKR superfamily, has furtherly verified that the stereospecificity of HSDHs was related to the substrate binding orientation.

Microbial Hydroxysteroid Dehydrogenases: From Alpha to Omega

Bile acids (BAs) and glucocorticoids are steroid hormones derived from cholesterol that are important signaling molecules in humans and other vertebrates. Hydroxysteroid dehydrogenases (HSDHs) are encoded both by the host and by their resident gut microbiota, and they reversibly convert steroid hydroxyl groups to keto groups. Pairs of HSDHs can reversibly epimerize steroids from α-hydroxy conformations to β-hydroxy, or β-hydroxy to ω-hydroxy in the case of ω-muricholic acid. These reactions often result in products with drastically different physicochemical properties than their precursors, which can result in steroids being activators or inhibitors of host receptors, can affect solubility in fecal water, and can modulate toxicity. Microbial HSDHs modulate sterols associated with diseases such as colorectal cancer, liver cancer, prostate cancer, and polycystic ovary syndrome. Although the role of microbial HSDHs is not yet fully elucidated, they may have therapeutic potential as steroid pool modulators or druggable targets in the future. In this review, we explore metabolism of BAs and glucocorticoids with a focus on biotransformation by microbial HSDHs.

Natural Mating Differentially Triggers Expression of Glucocorticoid Receptor (NR3C1)-Related Genes in the Preovulatory Porcine Female Reproductive Tract

Mating initiates dynamic modifications of gene transcription in the female reproductive tract, preparing the female for fertilization and pregnancy. Glucocorticoid signaling is essential for the homeostasis of mammalian physiological functions. This complex glucocorticoid regulation is mediated through the glucocorticoid receptor, also known as nuclear receptor subfamily 3 group C member 1 (NR3C1/GR) and related genes, like 11β-hydroxysteroid dehydrogenases (HSD11Bs) and the FK506-binding immunophilins, FKBP5 and FKBP4. This study tested the transcriptome changes in NR3C1/GR regulation in response to natural mating and/or cervical deposition of the sperm-peak ejaculate fraction collected using the gloved-hand method (semen or only its seminal plasma), in the preovulatory pig reproductive tract (cervix to infundibulum, 24 h after mating/insemination/infusion treatments). Porcine cDNA microarrays revealed 22 NR3C1-related transcripts, and changes in gene expression were triggered by all treatments, with natural mating showing the largest differences, including NR3C1, FKBP5, FKBP4, hydroxysteroid 11-beta dehydrogenase 1 and 2 (HSD11B1, HSD11B2), and the signal transducer and activator of transcription 5A (STAT5A). Our data suggest that natural mating induces expression changes that might promote a reduction of the cortisol action in the oviductal sperm reservoir. Together with the STAT-mediated downregulation of cytokine immune actions, this reduction may prevent harmful effects by promoting tolerance towards the spermatozoa stored in the oviduct and perhaps elicit spermatozoa activation and detachment after ovulation.

Laccase Did It again: A Scalable and Clean Regeneration System for NAD+ and Its Application in the Synthesis of 12-oxo-Hydroxysteroids

The specific oxidation of 12α-OH group of hydroxysteroids is required for the preparation of cheno- and ursodeoxycholic acid (CDCA and UDCA, respectively). The C12 oxidation of hydroxysteroids into their 12-oxo derivatives can selectively be performed by employing 12α-hydroxysteroid dehydrogenases. These enzymes use NAD(P)+ as an electron acceptor, which has to be re-oxidized in a so-called “regeneration system”. Recently, the enzyme NAD(P)H oxidase (NOX) was applied for the regeneration of NAD+ in the enzymatic preparation of 12-oxo-CDCA from cholic acid (CA), which allows air to be used as an oxidant. However, the NOX system suffers from low activity and low stability. Moreover, the substrate loading is limited to 10 mM. In this study, the laccase/mediator system was investigated as a possible alternative to NOX, employing air as an oxidant. The laccase/mediator system shows higher productivity and scalability than the NOX system. This was proven with a preparative biotransformation of 20 g of CA into 12-oxo-CDCA (92% isolated yield) by employing a substrate loading of 120 mM (corresponding to 50 g/L). Additionally, the performance of the laccase/mediator system was compared with a classical ADH/acetone regeneration system and with other regeneration systems reported in literature.