The devastating effects of the recent global pandemic (termed COVID-19 for “coronavirus disease 2019”) caused by the severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) are paramount with ...new cases and deaths growing at an exponential rate. In order to provide a better understanding of SARS CoV-2, this article will review the proteins found in the SARS CoV-2 that caused this global pandemic.
Many oxidation–reduction (redox) enzymes, particularly oxygenases, have roles in reactions that make and break C–C bonds. The list includes cytochrome P450 and other heme-based monooxygenases, ...heme-based dioxygenases, nonheme iron mono- and dioxygenases, flavoproteins, radical S-adenosylmethionine enzymes, copper enzymes, and peroxidases. Reactions involve steroids, intermediary metabolism, secondary natural products, drugs, and industrial and agricultural chemicals. Many C–C bonds are formed via either (i) coupling of diradicals or (ii) generation of unstable products that rearrange. C–C cleavage reactions involve several themes: (i) rearrangement of unstable oxidized products produced by the enzymes, (ii) oxidation and collapse of radicals or cations via rearrangement, (iii) oxygenation to yield products that are readily hydrolyzed by other enzymes, and (iv) activation of O2 in systems in which the binding of a substrate facilitates O2 activation. Many of the enzymes involve metals, but of these, iron is clearly predominant.
Aromatase is the cytochrome P450 enzyme that cleaves the C10–C19 carbon–carbon bond of androgens to form estrogens, in a three-step process. Compound I (FeO3+) and ferric peroxide (FeO2 –) have both ...been proposed in the literature as the active iron species in the third step, yielding an estrogen and formic acid. Incubation of purified aromatase with its 19-deutero-19-oxo androgen substrate was performed in the presence of 18O2, and the products were derivatized using a novel diazo reagent. Analysis of the products by high-resolution mass spectrometry showed a lack of 18O incorporation in the product formic acid, supporting only the Compound I pathway. Furthermore, a new androgen 19-carboxylic acid product was identified. The rates of nonenzymatic hydration of the 19-oxo androgen and dehydration of the 19,19-gem-diol were shown to be catalytically competent. Thus, the evidence supports Compound I and not ferric peroxide as the active iron species in the third step of the steroid aromatase reaction.
The global pandemic that shut down the world in 2020 was caused by the virus, SARS CoV-2. The chemistry of the various nonstructural proteins (NSP3, NSP5, NSP12, NSP13, NSP14, NSP15, NSP16) of SARS ...CoV-2 is discussed. Secondly, a recent major focus of this pandemic is the variant strains of SARS CoV-2 that are increasingly occurring and more transmissible. One strain, called “D614G”, possesses a glycine (G) instead of an aspartate (D) at position 614 of the spike protein. Additionally, other emerging strains called “501Y.V1” and “501Y.V2” have several differences in the receptor binding domain of the spike protein (N501Y) as well as other locations. These structural changes may enhance the interaction between the spike protein and the ACE2 receptor of the host, increasing infectivity. The global pandemic caused by SARS CoV-2 is a rapidly evolving situation, emphasizing the importance of continuing the efforts to interrogate and understand this virus.
Display omitted
•CYP17A1 catalyzes at least 13 different reactions with endogenous steroids.•Cytochrome b5 stimulates 17,20-lyase activity and enables andiene-β-synthase activity.•Metabolic switching ...occurs with deuterium labeled-progesterone substrates.•Minor products can have physiologic functions.
The steroid hydroxylation and carbon–carbon bond cleavage activities of cytochrome P450 17A1 (CYP17A1) are responsible for the production of glucocorticoids and androgens, respectively. The inhibition of androgen synthesis is an important strategy to treat androgen-dependent prostate cancer. We discuss the different enzymatic activities towards the various substrates of CYP17A1, demonstrating its promiscuity. Additionally, a novel interhelical interaction is proposed between the F–G loop and the B’-helix to explain the 16α-hydroxylase activity of human CYP17A1 with progesterone as the substrate. The techniques used by biochemists to study this important enzyme are also summarized.
This article is part of a Special Issue entitled 'Steroid/Sterol signaling'.
The human oxysterol 12α-hydroxylase cytochrome P450 8B1 (CYP8B1) is a validated drug target for both type 2 diabetes and nonalcoholic fatty liver disease, but effective selective inhibitors are not ...yet available. Herein, steroidal substrate-mimicking compounds with a pyridine ring appended to the C12 site of metabolism were designed as inhibitors, synthesized, and evaluated in terms of their functional and structural interactions with CYP8B1. While the pyridine nitrogen was intended to coordinate the CYP8B1 active site heme iron, none of these compounds elicited shifts in the CYP8B1 Soret absorbance consistent with this type of interaction. However, when CYP8B1 was cocrystallized with the pyridine-containing compound with the 3-keto-Δ4 steroid backbone most similar to the endogenous substrate, it was apparent that this ligand was bound in a channel leading to the active site, instead of near the heme iron. Inspection of this structure suggested that tryptophan 281 directly above the heme might restrict active site binding of potential inhibitors with this design. This hypothesis was supported when a CYP8B1 W281F mutation did allow all three compounds to coordinate the heme iron as designed. These results indicated that the design of next-generation CYP8B1 inhibitors should be compatible with the low-ceiling tryptophan immediately above the heme iron.
Artemisinin is the plant natural product used to treat malaria. The endoperoxide bridge of artemisinin confers its antiparasitic properties. Dihydroartemisinic acid is the biosynthetic precursor of ...artemisinin that was previously shown to nonenzymatically undergo endoperoxide formation to yield artemisinin. This report discloses the synthesis of 15,15,15-2H3-dihydroartemisinic acid and its use to determine the mechanism of endoperoxide formation. Several new observations were made: (i) Ultraviolet-C (UV-C) radiation initially accelerates artemisinin formation and subsequently promotes homolytic cleavage of the O–O bond and rearrangement of artemisinin to a different product, and (ii) dideuterated and trideuterated dihydroartemisinic acid isotopologues at C3 and C15 converted to artemisinin at a slower rate compared to nondeuterated dihydroartemisinic acid, revealing a kinetic isotope effect in the initial ene reaction toward endoperoxide formation (kH/kD ∼ 2–3). (iii) The rate of conversion from dihydroartemisinic acid to artemisinin increased with the amount of dihydroartemisinic acid, suggesting an intermolecular interaction to promote endoperoxide formation, and (iv) 18O2-labeling showed incorporation of three and four oxygen atoms from molecular oxygen into the endoperoxide bridge of artemisinin. These results reveal new insights toward understanding the mechanism of endoperoxide formation in artemisinin biosynthesis.
Cytochrome P450 (P450, CYP) 19A1 is the steroid aromatase, the enzyme responsible for the 3-step conversion of androgens (androstenedione or testosterone) to estrogens. The final step is C-C bond ...scission (removing the 19-oxo group as formic acid) that proceeds via a historically controversial reaction mechanism. The two competing mechanistic possibilities involve a ferric peroxide anion (Fe3+O2-, Compound 0) and a perferryl oxy species (FeO3+, Compound I). One approach to discern the role of each species in the reaction is with the use of oxygen-18 labeling, i.e., from 18O2 and H218O of the reaction product formic acid. We applied this approach, using several technical improvements, to study the deformylation of 19-oxo-androstenedione by human P450 19A1 and of a model secosteroid, 3-oxodecaline-4-ene-10-carboxaldehyde (ODEC), by rabbit P450 2B4. Both aldehyde substrates were sensitive to non-enzymatic acid-catalyzed deformylation, yielding 19-norsteroids, and conditions were established to avoid issues with artifactual generation of formic acid. The Compound 0 reaction pathway predominated (i.e., Fe3+O2-) in both P450 19A1 oxidation of 19-oxo-androstenedione and P450 2B4 oxidation of ODEC. The P450 19A1 results contrast with our prior conclusions (J. Am. Chem. Soc. 2014, 136, 15016-16025), attributed to several technical modifications.
Menarandroside A, which bears a 12α-hydroxypregnenolone steroid backbone, was isolated from the plant,
Cynanchum menarandrense
. Treatment of extracts from this plant containing menarandroside A ...against secretin tumor cell line (STC-1) intestinal cells, resulted in an increased secretion of glucagon-like peptide 1 (GLP-1), a peptide that plays a role in the regulation of blood sugar levels. Increase in GLP-1 is beneficial for the treatment of type 2 diabetes. We disclose the synthesis of menarandroside A from dehydroepiandrosterone (DHEA). Key features of this synthesis include: (i) Wittig reaction of the C17-ketone of a 12-oxygenated DHEA derivative to introduce the C17-acetyl moiety, and (ii) the stereoselective reduction of a C12-keto intermediate bearing an sp
2
-center at C17 to yield the C12α-hydroxy group. In addition, an oxidation of a methyl enol ether derivative to an α-hydroxy methyl ester using tetrapropylammonium perruthenate (TPAP) and
N
-methyl-morpholine-
N
-oxide (NMO) was discovered.
Menarandroside A, which bears a 12-hydroxypregnenolone steroid backbone, was isolated from the plant,
Cynanchum menarandrense
. This natural product was synthesized from dehydroepiandrosterone (DHEA).
Display omitted
•Hyocholic acid was synthesized from chenodeoxycholic acid.•X-ray crystal structure confirmed C6-alpha-hydroxy stereochemistry.•A derivatization method using NaIO4 was developed to ...distinguish hyocholic acid from cholic acid.•Application of the derivatization method to detect hyocholic acid derivatives in ox bile.
Low concentrations of hyocholic acid in human serum has been linked to diabetes. Due to its important role in human health, we were interested in synthesizing hyocholic acid to explore potential biochemical properties of this bile acid. Here, a synthesis of hyocholic acid is reported from chenodeoxycholic acid. The key step was a Rubottom oxidation of a silyl enol ether intermediate to directly incorporate the oxygen at C6. Furthermore, the synthesized hyocholic acid product was treated with NaIO4 to cleave the C6-C7 bond to yield a hemiacetal at C6. This CC bond cleavage reaction using NaIO4 was used to develop an ultra-performance liquid chromatography mass spectrometry method to distinguish between a 1 to 1 mixture of hyocholic acid and cholic acid (a 12α-hydroxylated bile acid), two bile acid regioisomers with identical masses. Upon treatment of the mixture with NaIO4, hyocholic acid was selectively cleaved in the B ring (C6-C7 bond) to yield the hemiacetal that formed between the C3-hydroxy and the C6-aldehyde moiety with an m/z 405 while cholic acid remained intact with an m/z 407 in the negative electrospray ionization mode. Subsequently, a commercially available ox bile extract was treated with NaIO4 to detect bile acid derivatives by mass spectrometry. Two possible hyocholic acid derivatives conjugated to serine and gamma-glutamic semialdehyde were detected in electrospray ionization positive mode, which oxidatively cleaved with NaIO4 (m/z 496 and 522 to m/z 494 and 520, respectively).
PDF
![Synthesis of [15,15,15‑2H3]...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0163-3864_1520-6025/small "Synthesis of [15,15,15‑2H3]‑Dihydroartemisinic Acid and Isotope Studies Support a Mixed Mechanism in the Endoperoxide Formation to Artemisinin")
