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Human steroid 5α-reductase 2 (SRD5A2) is an integral membrane enzyme in steroid metabolism and catalyzes the reduction of testosterone to dihydrotestosterone. Mutations in the SRD5A2 gene have been linked to 5α-reductase deficiency and prostate cancer. Finasteride and dutasteride, as SRD5A2 inhibitors, are widely used antiandrogen drugs for benign prostate hyperplasia. The molecular mechanisms underlying enzyme catalysis and inhibition for SRD5A2 and other eukaryotic integral membrane steroid reductases remain elusive due to a lack of structural information. Here, we report a crystal structure of human SRD5A2 at 2.8 Å, revealing a unique 7-TM structural topology and an intermediate adduct of finasteride and NADPH as NADP-dihydrofinasteride in a largely enclosed binding cavity inside the transmembrane domain. Structural analysis together with computational and mutagenesis studies reveal the molecular mechanisms of the catalyzed reaction and of finasteride inhibition involving residues E57 and Y91. Molecular dynamics simulation results indicate high conformational dynamics of the cytosolic region that regulate NADPH/NADP + exchange. Mapping disease-causing mutations of SRD5A2 to our structure suggests molecular mechanisms for their pathological effects. Our results offer critical structural insights into the function of integral membrane steroid reductases and may facilitate drug development. Human steroid 5α-reductase 2 (SRD5A2) is an integral membrane enzyme and catalyzes 5α-reduction of testosterone to dihydrotestosterone. Structural analysis accompanied by computational and mutagenesis studies reveal the mechanisms of catalysis and inhibition by clinically relevant drugs targeting SRD5A2.

Steroid hormones are essential in stress response, immune system regulation, and reproduction in mammals. Steroids with 3-oxo-Δ 4 structure, such as testosterone or progesterone, are catalyzed by steroid 5α-reductases (SRD5As) to generate their corresponding 3-oxo-5α steroids, which are essential for multiple physiological and pathological processes. SRD5A2 is already a target of clinically relevant drugs. However, the detailed mechanism of SRD5A-mediated reduction remains elusive. Here we report the crystal structure of PbSRD5A from Proteobacteria bacterium , a homolog of both SRD5A1 and SRD5A2, in complex with the cofactor NADPH at 2.0 Å resolution. PbSRD5A exists as a monomer comprised of seven transmembrane segments (TMs). The TM1-4 enclose a hydrophobic substrate binding cavity, whereas TM5-7 coordinate cofactor NADPH through extensive hydrogen bonds network. Homology-based structural models of HsSRD5A1 and -2, together with biochemical characterization, define the substrate binding pocket of SRD5As, explain the properties of disease-related mutants and provide an important framework for further understanding of the mechanism of NADPH mediated steroids 3-oxo-Δ 4 reduction. Based on these analyses, the design of therapeutic molecules targeting SRD5As with improved specificity and therapeutic efficacy would be possible. Steroid 5α-reductase 2 (SRD5A2), a testosterone metabolism enzyme, is implicated in human disease. Structural and biochemical analyses of PbSRD5A, a bacterial homolog, reveal SRD5A2 substrate binding pocket and provide framework for the design of new drugs targeting this enzyme.

Background Disorders of sex development (DSDs) exhibit high genetic and phenotypic heterogeneity, and genotype–phenotype correlations are not fully understood. 5α-Reductase type 2 (5α-RD2) deficiency, a common form of DSD, is caused by SRD5A2 inactivation. This study investigated the role of SRD5A2 haplotypes in DSD, focusing on their corresponding phenotypes, structural changes and impacts on enzyme activity. Methods This study enrolled 216 individuals with DSD who underwent genetic analysis and 2,794 controls. Linkage disequilibrium analysis was performed in individuals with 5α-RD2 deficiency to identify SRD5A2 haplotypes, and haplotype frequencies were analysed across cohorts. The clinical manifestations of individuals with different SRD5A2 haplotypes were characterized. Structural predictions were employed to investigate the impacts of haplotypes on the 5α-RD2 structure and interactions with ligands. Functionally, kinetic assays were conducted to validate the effects of different haplotypes on enzyme activity. Results A SRD5A2 haplotype composed of c.265C > G and c.680G > A (Hap3: G-A) was identified, and the haplotype frequency was 64.71% in individuals with 5α-RD2 deficiency, 2.59% and 1.22% in non-5α-RD2 deficiency DSD cases without or with known DSD-related gene variants, respectively, and 1.57% in in-house controls. Globally, Hap3: G-A was enriched in southern Chinese individuals and showed high population differentiation, indicating a potential founder effect of the haplotype. The majority of homozygotes of Hap3: G-A presented microphallus, and nearly half of them manifested isolated microphallus. Structurally, Hap3: G-A was predicted to result in an increase in the solvent-accessible surface area (10.72 Å 2 ), a redistribution of hydrogen bonds within 5α-RD2, and a loss of key hydrogen bonds with NADPH. Functionally, kinetic assays showed that the catalytic efficiency of the enzyme encoded by Hap3: G-A was between that of Hap1: G-G and that of Hap2: C-A. Conclusions Hap3: G-A, which is prevalent in individuals with 5α-RD2 deficiency, suggests a potential founder effect. Structurally, compared with other haplotypes, Hap3: G-A seems to have a combined effect on the structure and interaction of 5α-RD2, rather than have merely additive effects of its constituent variants. Functionally, kinetic assays suggested a hypomorphic effect of Hap3: G-A. These findings provide valuable insights for understanding genotype–phenotype correlations, genetic counselling, early intervention and clinical management of individuals with 5α-RD2 deficiency or even other DSDs. Highlights On the basis of 216 DSD individuals and 2,794 controls, a novel SRD5A2 haplotype (Hap3: G-A), which is composed of common variants and is especially prevalent in DSD patients with 5α-RD2 deficiency, was identified, indicating the potential founder effect of Hap3: G-A. The majority of 5α-RD2 deficiency individuals with homozygous Hap3: G-A presented microphallus. Three-dimensional structure and model construction predicted that Hap3: G-A resulted in an increase in the solvent-accessible surface area, redistribution of hydrogen bonds within 5α-RD2, and loss of key hydrogen bonds with NADPH. Functionally, kinetic assays showed that the catalytic efficiency of the enzyme encoded by Hap3: G-A was between those of Hap1: G-G and Hap2: C-A, suggesting a hypomorphic effect of this haplotype. Plain Language Summary Individuals with disorders of sex development (DSDs) present variable genotypes and phenotypes, and the genotype–phenotype correlation remains poorly understood. 5α-Reductase type 2 (5α-RD2) deficiency, a common form of DSD, is caused by SRD5A2 inactivation. In this study, genetic testing and analysis were performed in 216 individuals with DSD and 2,794 non-DSD controls. A novel SRD5A2 haplotype (Hap3: G-A) was identified, and the haplotype frequency was 64.71% in individuals with 5α-RD2 deficiency, 2.59% and 1.22% in non-5α-RD2 deficiency DSD cases without or with known DSD-related gene variants, respectively, and 1.57% in in-house controls. Globally, Hap3: G-A was enriched in southern Chinese individuals and showed high population differentiation, indicating a potential founder effect of the haplotype. Analyzing the phenotype spectrum of individuals with 5α-RD2 deficiency, we found that the majority of homozygotes of Hap3: G-A presented microphallus, and nearly half of them manifested isolated microphallus. Structurally, Hap3: G-A was predicted to result in an increase in the solvent-accessible surface area, the redistribution of hydrogen bonds within 5α-RD2, and the loss of key hydrogen bonds with NADPH. Compared with other haplotypes, Hap3: G-A seemed to have a combined effect on the structure and interaction of 5α-RD2, rather than simply additive effects of its constituent variants. Functionally, kinetic assays showed that the catalytic efficiency of the enzyme encoded by Hap3: G-A was between that of Hap1: G-G and that of Hap2: C-A, suggesting a hypomorphic effect of this haplotype. These findings provide valuable insights for understanding genotype–phenotype correlations, genetic counselling, early intervention and clinical management of individuals with 5α-RD2 deficiency or even other DSDs.

This work investigated the spectrum-effect relationships between high performance liquid chromatography (HPLC) fingerprints and the anti-benign prostatic hyperplasia activities of aqueous extracts from Saxifraga stolonifera. The fingerprints of S. stolonifera from various sources were established by HPLC and evaluated by similarity analysis (SA), hierarchical clustering analysis (HCA) and principal component analysis (PCA). Nine samples were obtained from these 24 batches of different origins, according to the results of SA, HCA and the common chromatographic peaks area. A testosterone-induced mouse model of benign prostatic hyperplasia (BPH) was used to establish the anti-benign prostatic hyperplasia activities of these nine S. stolonifera samples. The model was evaluated by analyzing prostatic index (PI), serum acid phosphatase (ACP) activity, concentrations of serum dihydrotestosterone (DHT), prostatic acid phosphatase (PACP) and type II 5α-reductase (SRD5A2). The spectrum-effect relationships between HPLC fingerprints and anti-benign prostatic hyperplasia activities were investigated using Grey Correlation Analysis (GRA) and partial least squares regression (PLSR). The results showed that a close correlation existed between the fingerprints and anti-benign prostatic hyperplasia activities, and peak 14 (chlorogenic acid), peak 17 (quercetin 5-O-β-d-glucopyranoside) and peak 18 (quercetin 3-O-β-l-rhamno-pyranoside) in the HPLC fingerprints might be the main active components against anti-benign prostatic hyperplasia. This work provides a general model for the study of spectrum-effect relationships of S. stolonifera by combing HPLC fingerprints with a testosterone-induced mouse model of BPH, which can be employed to discover the principle components of anti-benign prostatic hyperplasia bioactivity.

Steroid 5α-reductase type 3 congenital disorder of glycosylation (SRD5A3-CDG) is a severe metabolic disease manifesting as muscle hypotonia, developmental delay, cerebellar ataxia and ocular symptoms; typically, nystagmus and optic disc pallor. Recently, early onset retinal dystrophy has been reported as an additional feature. In this study, we summarize ocular phenotypes and SRD5A3 variants reported to be associated with SRD5A3-CDG. We also describe in detail the ophthalmic findings in a 12-year-old Czech child harbouring a novel homozygous variant, c.436G>A, p.(Glu146Lys) in SRD5A3 . The patient was reviewed for congenital nystagmus and bilateral optic neuropathy diagnosed at 13 months of age. Examination by spectral domain optical coherence tomography and fundus autofluorescence imaging showed clear signs of retinal dystrophy not recognized until our investigation. Best corrected visual acuity was decreased to 0.15 and 0.16 in the right and left eye, respectively, with a myopic refractive error of –3.0 dioptre sphere (DS) / –2.5 dioptre cylinder (DC) in the right and –3.0 DS / –3.0 DC in the left eye. The proband also had optic head nerve drusen, which have not been previously observed in this syndrome.

Although steroid hormones are important for animal development, the physiological role of plant steroids is unknown. The Arabidopsis DET2 gene encodes a protein that shares significant sequence identity with mammalian steroid 5 alpha-reductases. A mutation of glutamate 204, which is absolutely required for the activity of human steroid reductase, abolishes the in vivo activity of DET2 and leads to defects in light-regulated development that can be ameliorated by application of a plant steroid, brassinolide. Thus, DET2 may encode a reductase in the brassinolide biosynthetic pathway, and brassinosteroids may constitute a distinct class of phytohormones with an important role in light-regulated development of higher plants

The steroid 5α-reductase type II enzyme catalyzes the conversion of testosterone (T) to dihydrotestosterone (DHT), and its deficiency leads to undervirilization in 46,XY individuals, due to an impairment of this conversion in genital tissues. Molecular analysis in the steroid 5α-reductase type II gene (SRD5A2) was performed in two 46,XY female siblings. SRD5A2 gene sequencing revealed that the patients were homozygous for p.Gln126Arg missense mutation, which results from the CGA > CAA nucleotide substitution. The molecular result confirmed clinical diagnosis of 46,XY disorder of sex development (DSD) for the older sister and directed the investigation to other family members. Studies on SRD5A2 protein structure showed severe changes at NADPH binding region indicating that structural modeling analysis can be useful to evaluate the deleterious role of a mutation as causing 5α-reductase type II enzyme deficiency.

5-Alpha-reductase 2 is an interesting pharmaceutical target for the treatment of several diseases, including prostate cancer, benign prostatic hyperplasia, male pattern baldness, acne, and hirsutism. One of the main approaches in computer aided drug design is structure-based drug discovery. However, the experimental 3D structure of 5-alpha-reductase 2 is not available at present. Therefore, a homology modeling method and molecular dynamics simulation were used to develop a reliable model of 5-alpha-reductase 2 for inhibitor pose prediction and virtual screening. Despite the low sequence identity between the target and template sequences, a useful 3D model of 5-alpha-reductase 2 was generated by the inclusion of experimental data.

The synthesis and evaluation of 5α-reductase inhibitory activity of some 4-azasteroid-20-ones and 20-oximes and 3β-hydroxy-, 3β-acetoxy-, or epoxy-substituted C21 steroidal 20-ones and 20-oximes having double bonds in the A and/or B ring are described. Inhibitory activity of synthesized compounds was assessed using 5α-reductase enzyme and [1,2,6,7-3H]testosterone as substrate. All synthesized compounds were less active than finasteride (IC50: 1.2 nM). Three 4-azasteroid-2-oximes (compounds 4, 6 and 8) showed good inhibitory activity (IC50: 26, 10 and 11 nM) and were more active than corresponding 4-azasteroid 20-ones (compounds 3, 5 and 7). 3β-Hydroxy-, 3β-acetoxy- and 1α,2α-, 5α,6α- or 6α,7α-epoxysteroid-20-one and -20-oxime derivatives having double bonds in the A and/or B ring showed no inhibition of 5α-reductase enzyme.

Plants do not use steroid hormones for intercellular communication. In his Perspective, D. Russell describes how this truism is now proven incorrect by two papers—one in this week's issue of Science (Li et al ., p. 398 ) and one in the 19 April issue of Cell (M. Szekeres et al .)—in which two enzymes that synthesize steroid hormones are cloned from Arabidopsis . These enzymes, DET2 and CPD, are in the biosynthetic pathway for brassinolides, steroids that seem to participate in the regulation of gene expression by light.