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Chemico-biological Interactions Jun 2015The aldo-keto reductase (AKR) protein superfamily contains >190 members that fall into 16 families and are found in all phyla. These enzymes reduce carbonyl substrates... (Review)
Review
The aldo-keto reductase (AKR) protein superfamily contains >190 members that fall into 16 families and are found in all phyla. These enzymes reduce carbonyl substrates such as: sugar aldehydes; keto-steroids, keto-prostaglandins, retinals, quinones, and lipid peroxidation by-products. Exceptions include the reduction of steroid double bonds catalyzed by AKR1D enzymes (5β-reductases); and the oxidation of proximate carcinogen trans-dihydrodiol polycyclic aromatic hydrocarbons; while the β-subunits of potassium gated ion channels (AKR6 family) control Kv channel opening. AKRs are usually 37kDa monomers, have an (α/β)8-barrel motif, display large loops at the back of the barrel which govern substrate specificity, and have a conserved cofactor binding domain. AKRs catalyze an ordered bi bi kinetic mechanism in which NAD(P)H cofactor binds first and leaves last. In enzymes that favor NADPH, the rate of release of NADP(+) is governed by a slow isomerization step which places an upper limit on kcat. AKRs retain a conserved catalytic tetrad consisting of Tyr55, Asp50, Lys84, and His117 (AKR1C9 numbering). There is conservation of the catalytic mechanism with short-chain dehydrogenases/reductases (SDRs) even though they show different protein folds. There are 15 human AKRs of these AKR1B1, AKR1C1-1C3, AKR1D1, and AKR1B10 have been implicated in diabetic complications, steroid hormone dependent malignancies, bile acid deficiency and defects in retinoic acid signaling, respectively. Inhibitor programs exist world-wide to target each of these enzymes to treat the aforementioned disorders. Inherited mutations in AKR1C and AKR1D1 enzymes are implicated in defects in the development of male genitalia and bile acid deficiency, respectively, and occur in evolutionarily conserved amino acids. The human AKRs have a large number of nsSNPs and splice variants, but in many instances functional genomics is lacking. AKRs and their variants are now poised to be interrogated using modern genomic and informatics approaches to determine their association with human health and disease.
Topics: Aldehyde Reductase; Aldo-Keto Reductases; Catalysis; Fatty Acid Synthases; Humans; NADH, NADPH Oxidoreductases; NADP; Oxidation-Reduction; Protein Structure, Tertiary; Steroids; Substrate Specificity
PubMed: 25304492
DOI: 10.1016/j.cbi.2014.09.024 -
Journal of the American Heart... Mar 2022Background Preeclampsia, a leading cause of maternal and fetal mortality and morbidity, is characterized by an increase in S-nitrosylated proteins and reactive oxygen...
Background Preeclampsia, a leading cause of maternal and fetal mortality and morbidity, is characterized by an increase in S-nitrosylated proteins and reactive oxygen species, suggesting a pathophysiologic role for dysregulation in nitrosylation and nitrosative stress. Methods and Results Here, we show that mice lacking S-nitrosoglutathione reductase (), a denitrosylase regulating protein S-nitrosylation, exhibit a preeclampsia phenotype, including hypertension, proteinuria, renal pathology, cardiac concentric hypertrophy, decreased placental vascularization, and fetal growth retardation. Reactive oxygen species, NO, and peroxynitrite levels are elevated. Importantly, mass spectrometry reveals elevated placental S-nitrosylated amino acid residues in mice. Ascorbate reverses the phenotype except for fetal weight, reduces the difference in the S-nitrosoproteome, and identifies a unique set of S-nitrosylated proteins in mice. Importantly, human preeclamptic placentas exhibit decreased GSNOR activity and increased nitrosative stress. Conclusions Therefore, deficiency of GSNOR creates dysregulation of placental S-nitrosylation and preeclampsia in mice, which can be rescued by ascorbate. Coupled with similar findings in human placentas, these findings offer valuable insights and therapeutic implications for preeclampsia.
Topics: Alcohol Dehydrogenase; Aldehyde Oxidoreductases; Animals; Female; Mice; Nitric Oxide; Placenta; Pre-Eclampsia; Pregnancy; Reactive Oxygen Species
PubMed: 35191317
DOI: 10.1161/JAHA.121.024008 -
Methods in Enzymology 2023In mammals there are two 3-oxo-4-ene steroid reductases that generate either A/B-trans or A/B cis-ring junctions in the steroid nucleus known as steroid 5α- and 5β-...
In mammals there are two 3-oxo-4-ene steroid reductases that generate either A/B-trans or A/B cis-ring junctions in the steroid nucleus known as steroid 5α- and 5β- reductases, respectively. There is only one steroid 5β- reductase in each species and these are members of the aldo-keto-reductase (AKR) protein superfamily. The corresponding human enzyme is AKR1D1, and it plays an essential role in bile-acid biosynthesis. Germline mutations in AKR1D1 give rise to bile-acid deficiency. Because of its central role in steroid metabolism and need for detailed structure-function studies there is a need to purify the enzyme to homogeneity and in high yield. We report the purification of milligram amounts of crystallographic quality homogeneous recombinant protein for structure-function studies and its characterization.
Topics: Animals; Humans; Oxidoreductases; Steroids; Bile Acids and Salts; Mammals
PubMed: 37802574
DOI: 10.1016/bs.mie.2023.04.012 -
The Journal of Biological Chemistry Dec 2022The cytochrome-b reductase (CYB5R) family of flavoproteins is known to regulate reduction-oxidation (redox) balance in cells. The five enzyme members are highly... (Review)
Review
The cytochrome-b reductase (CYB5R) family of flavoproteins is known to regulate reduction-oxidation (redox) balance in cells. The five enzyme members are highly compartmentalized at the subcellular level and function as "redox switches" enabling the reduction of several substrates, such as heme and coenzyme Q. Critical insight into the physiological and pathophysiological significance of CYB5R enzymes has been gleaned from several human genetic variants that cause congenital disease and a broad spectrum of chronic human diseases. Among the CYB5R genetic variants, CYB5R3 is well-characterized and deficiency in expression and activity is associated with type II methemoglobinemia, cancer, neurodegenerative disorders, diabetes, and cardiovascular disease. Importantly, pharmacological and genetic-based strategies are underway to target CYB5R3 to circumvent disease onset and mitigate severity. Despite our knowledge of CYB5R3 in human health and disease, the other reductases in the CYB5R family have been understudied, providing an opportunity to unravel critical function(s) for these enzymes in physiology and disease. In this review, we aim to provide the broad scientific community an up-to-date overview of the molecular, cellular, physiological, and pathophysiological roles of CYB5R proteins.
Topics: Humans; Cytochrome-B(5) Reductase; Cytochromes b5; Methemoglobinemia; Oxidation-Reduction; Homeostasis; Cytochrome Reductases
PubMed: 36441026
DOI: 10.1016/j.jbc.2022.102654 -
Endocrine Reviews Apr 2019Aldo-keto reductases (AKRs) are monomeric NAD(P)(H)-dependent oxidoreductases that play pivotal roles in the biosynthesis and metabolism of steroids in humans. AKR1C... (Review)
Review
Aldo-keto reductases (AKRs) are monomeric NAD(P)(H)-dependent oxidoreductases that play pivotal roles in the biosynthesis and metabolism of steroids in humans. AKR1C enzymes acting as 3-ketosteroid, 17-ketosteroid, and 20-ketosteroid reductases are involved in the prereceptor regulation of ligands for the androgen, estrogen, and progesterone receptors and are considered drug targets to treat steroid hormone-dependent malignancies and endocrine disorders. In contrast, AKR1D1 is the only known steroid 5β-reductase and is essential for bile-acid biosynthesis, the generation of ligands for the farnesoid X receptor, and the 5β-dihydrosteroids that have their own biological activity. In this review we discuss the crystal structures of these AKRs, their kinetic and catalytic mechanisms, AKR genomics (gene expression, splice variants, polymorphic variants, and inherited genetic deficiencies), distribution in steroid target tissues, roles in steroid hormone action and disease, and inhibitor design.
Topics: Aldo-Keto Reductases; Humans; Hydroxysteroid Dehydrogenases; Oxidoreductases; Steroids
PubMed: 30137266
DOI: 10.1210/er.2018-00089 -
Redox Biology Jan 2021Cellular antioxidants protect against hyperoxic lung injury. The role of the glutathione (GSH) system in lung development and bronchopulmonary dysplasia (BPD)...
Cellular antioxidants protect against hyperoxic lung injury. The role of the glutathione (GSH) system in lung development and bronchopulmonary dysplasia (BPD) pathogenesis has not been systematically investigated. The current study utilized GSH reductase-deficient (Gsr-KO) neonatal mice to test the hypothesis that early disruption of the GSH system negatively impacts lung development and hyperoxic responses. Lungs from wild-type (Gsr-WT) and Gsr-KO mice were analyzed for histopathology, developmental markers, redox indices, and transcriptome profiling at different developmental stages following exposure to room air or hyperoxia (85% O) for up to 14 d. Lungs from Gsr-KO mice exhibited alveolar epithelial dysplasia in the embryonic and neonatal periods with relatively normal lung architecture in adulthood. GSH and its oxidized form (GSSG) were 50-70% lower at E19-PND14 in Gsr-KO lungs than in age-matched Gsr-WT. Differential gene expression between Gsr-WT and Gsr-KO lungs was analyzed at discrete developmental stages. Gsr-KO lungs exhibited downregulated cell cycle and DNA damage checkpoint genes at E19, as well as lung lipid metabolism and surfactant genes at PND5. In addition to abnormal baseline lung morphometry, Gsr-KO mice displayed a blunted response to hyperoxia. Hyperoxia caused a more robust upregulation of the lung thioredoxin system in Gsr-KO compared to Gsr-WT. Gsr-dependent, hyperoxia-responsive genes were highly associated with abnormal cytoskeleton, skeletal-muscular function, and tissue morphology at PND5. Overall, our data in Gsr-KO mice implicate the GSH system as a key regulator of lung development, cellular differentiation, and hyperoxic responses in neonatal mice.
Topics: Animals; Animals, Newborn; Glutathione; Glutathione Reductase; Hyperoxia; Lung; Mice; Oxidoreductases
PubMed: 33254076
DOI: 10.1016/j.redox.2020.101797 -
The Journal of Clinical Investigation Jul 2022Mitochondrial DNA (mtDNA) depletion/deletions syndromes (MDDS) encompass a clinically and etiologically heterogenous group of mitochondrial disorders caused by impaired...
Mitochondrial DNA (mtDNA) depletion/deletions syndromes (MDDS) encompass a clinically and etiologically heterogenous group of mitochondrial disorders caused by impaired mtDNA maintenance. Among the most frequent causes of MDDS are defects in nucleoside/nucleotide metabolism, which is critical for synthesis and homeostasis of the deoxynucleoside triphosphate (dNTP) substrates of mtDNA replication. A central enzyme for generating dNTPs is ribonucleotide reductase, a critical mediator of de novo nucleotide synthesis composed of catalytic RRM1 subunits in complex with RRM2 or p53R2. Here, we report 5 probands from 4 families who presented with ptosis and ophthalmoplegia as well as other clinical manifestations and multiple mtDNA deletions in muscle. We identified 3 RRM1 loss-of-function variants, including a dominant catalytic site variant (NP_001024.1: p.N427K) and 2 homozygous recessive variants at p.R381, which has evolutionarily conserved interactions with the specificity site. Atomistic molecular dynamics simulations indicate mechanisms by which RRM1 variants affect protein structure. Cultured primary skin fibroblasts of probands manifested mtDNA depletion under cycling conditions, indicating impaired de novo nucleotide synthesis. Fibroblasts also exhibited aberrant nucleoside diphosphate and dNTP pools and mtDNA ribonucleotide incorporation. Our data reveal that primary RRM1 deficiency and, by extension, impaired de novo nucleotide synthesis are causes of MDDS.
Topics: DNA Replication; DNA, Mitochondrial; Humans; Mitochondrial Diseases; Nucleosides; Nucleotides; Ribonucleoside Diphosphate Reductase; Ribonucleotide Reductases
PubMed: 35617047
DOI: 10.1172/JCI145660 -
Δ4-3-oxosteroid-5β-reductase deficiency: Responses to oral bile acid therapy and long-term outcomes.World Journal of Gastroenterology Feb 2019Disorders of primary bile acid synthesis may be life-threatening if undiagnosed, or not treated with primary bile acid replacement therapy. To date, there are few...
BACKGROUND
Disorders of primary bile acid synthesis may be life-threatening if undiagnosed, or not treated with primary bile acid replacement therapy. To date, there are few reports on the management and follow-up of patients with Δ4-3-oxosteroid 5β-reductase (AKR1D1) deficiency. We hypothesized that a retrospective analysis of the responses to oral bile acid replacement therapy with chenodeoxycholic acid (CDCA) in patients with this bile acid synthesis disorder will increase our understanding of the disease progression and permit evaluation of this treatment regimen as an alternative to the Food and Drug Administration (FDA) approved drug cholic acid, which is currently unavailable in China.
AIM
To evaluate the therapeutic responses of patients with AKR1D1 deficiency to oral bile acid therapy, specifically CDCA.
METHODS
Twelve patients with AKR1D1 deficiency, confirmed by fast atom bombardment ionization-mass spectrometry analysis of urine and by gene sequencing for mutations in , were treated with differing doses of CDCA or ursodeoxycholic acid (UDCA). The clinical and biochemical responses to therapy were monitored over a period ranging 0.5-6.4 years. Dose adjustment, to optimize the therapeutic dose, was based on changes in serum biochemistry parameters, notably liver function tests, and suppression of the urinary levels of atypical hepatotoxic 3-oxo-Δ4-bile acids measured by mass spectrometry.
RESULTS
Physical examination, serum biochemistry parameters, and sonographic findings improved in all 12 patients during bile acid therapy, except one who underwent liver transplantation. Urine bile acid analysis confirmed a significant reduction in atypical hepatotoxic 3-oxo-Δ4 bile acids concomitant with clinical and biochemical improvements in those patients treated with CDCA. UDCA was ineffective in down-regulating endogenous bile acid synthesis as evidenced from the inability to suppress the urinary excretion of atypical 3-oxo-Δ4-bile acids. The dose of CDCA required for optimal clinical and biochemical responses varied from 5.5-10 mg/kg per day among patients based on maximum suppression of the atypical bile acids and improvement in serum biochemistry parameters, and careful titration of the dose was necessary to avoid side effects from CDCA.
CONCLUSION
The primary bile acid CDCA is effective in treating AKR1D1 deficiency but the therapeutic dose requires individualized optimization. UDCA is not recommended for long-term management.
Topics: Administration, Oral; Chenodeoxycholic Acid; DNA Mutational Analysis; Disease Progression; Dose-Response Relationship, Drug; Female; Gastrointestinal Agents; Humans; Infant, Newborn; Male; Metabolic Diseases; Mutation; Oxidoreductases; Retrospective Studies; Treatment Outcome; Ursodeoxycholic Acid
PubMed: 30809085
DOI: 10.3748/wjg.v25.i7.859 -
Psychotherapy and Psychosomatics 2003
Topics: Depressive Disorder; Folic Acid Deficiency; Humans; Methylenetetrahydrofolate Reductase (NADPH2); Oxidoreductases Acting on CH-NH Group Donors; Polymorphism, Genetic
PubMed: 12601222
DOI: 10.1159/000068693 -
Steroids May 20145β-Reduced steroids are non-planar steroids that have a 90° bend in their structure to create an A/B cis-ring junction. This novel property is required for bile-acids... (Review)
Review
5β-Reduced steroids are non-planar steroids that have a 90° bend in their structure to create an A/B cis-ring junction. This novel property is required for bile-acids to act as emulsifiers, but in addition 5β-reduced steroids have remarkable physiology and may act as potent tocolytic agents, endogenous cardiac glycosides, neurosteroids, and can act as ligands for orphan and membrane bound receptors. In humans there is only a single 5β-reductase gene AKR1D1, which encodes Δ(4)-3-ketosteroid-5β-reductase (AKR1D1). This enzyme is a member of the aldo-keto reductase superfamily, but possesses an altered catalytic tetrad, in which Glu120 replaces the conserved His residue. This predominant liver enzyme generates all 5β-dihydrosteroids in the C19-C27 steroid series. Mutations exist in the AKR1D1 gene, which result in loss of protein stability and are causative in bile-acid deficiency.
Topics: Gene Expression Profiling; Humans; Oxidation-Reduction; Oxidoreductases; Steroids
PubMed: 24513054
DOI: 10.1016/j.steroids.2014.01.013