Initiation, Propagation, and Termination in the Chemistry of Radical SAM Enzymes.

Radical -adenosyl-l-methionine (SAM) enzymes catalyze radical mediated chemical transformations notable for their diversity. The radical mediated reactions that take place in their catalytic cycles can be characterized with respect to one or more phases of initiation, propagation, and termination. Mechanistic models abound regarding these three phases of catalysis being regularly informed and updated by new discoveries that offer insights into their detailed workings.

Elevated Plasma IL-6 Coincides with Activation of STAT3 in PBMC After Acute Resistance Exercise.

Introduction: Changes in plasma concentrations of anti-inflammatory cytokines, such as interleukin-6 (IL-6) and IL-10, after acute resistance exercise (RE) have been widely explored. Whether observed changes in plasma cytokine concentration correspond to the activation of anti-inflammatory signaling pathways in immune cells after acute RE is unknown. This study aimed to determine if changes in plasma cytokines after acute RE resulted in the activation of anti-inflammatory signaling pathways in peripheral blood mononuclear cells (PBMC).

In Vitro Characterization of Kitasetaline Biosynthesis Reveals a Bifunctional P450 Decarboxylase and a Vinyl β-Carboline Intermediate Susceptible to Nonenzymatic Thiol Addition.

Kitasetaline is one of the very few β-carbolines isolated from bacteria. It features a unique -acetylcysteine moiety linked to the β-carboline core through a thioether bond. While earlier experiments identified the gene cluster and reported several putative biosynthetic intermediates, how the C-S bond linkage is constructed has remained elusive.

Expression, purification and characterization of non-heme iron-dependent mono-oxygenase OzmD in oxazinomycin biosynthesis.

Oxazinomycin is a C-nucleoside natural product characterized by a 1,3-oxazine ring linked to ribose via a C-C glycosidic bond. Construction of the 1,3-oxazine ring depends on the activity of OzmD, which is a mononuclear non-heme iron-dependent enzyme from a family of enzymes that contain a domain of unknown function (DUF) 4243. OzmD catalyzes an unusual oxidative ring rearrangement of a pyridine derivative that releases cyanide as a by-product in the final stage of oxazinomycin biosynthesis.

Biosynthesis of the Unusual Epoxy Isonitrile-Containing Antibiotics Aerocyanidin and Amycomicin.

Aerocyanidin and amycomicin are two antibiotics derived from long-chain acids with a rare epoxy isonitrile moiety, the complexity of which renders the total synthesis of these two natural products rather challenging. How this functionality is biosynthesized has also remained obscure. While the biosynthetic gene clusters for these compounds have been identified, both appear to be deficient in genes encoding enzymes seemingly necessary for the oxidative modifications observed in these antibiotics.

Fluorogenic Aptamer Optimizations on a Massively Parallel Sequencing Platform.

F luorogenic ap tamers (FAPs) have become an increasingly important tool in cellular sensing and pathogen diagnostics. However, fine-tuning FAPs for enhanced performance remains challenging even with the structural details provided by X-ray crystallography. Here we present a novel approach to optimize a DNA-based FAP (D-FAP), Lettuce, on repurposed Illumina next-generation sequencing (NGS) chips.

Mechanistic Insights from the Crystal Structure and Computational Analysis of the Radical SAM Deaminase DesII.

Radical S-adenosyl-L-methionine (SAM) enzymes couple the reductive cleavage of SAM to radical-mediated transformations that have proven to be quite broad in scope. DesII is one such enzyme from the biosynthetic pathway of TDP-desosamine where it catalyzes a radical-mediated deamination. Previous studies have suggested that this reaction proceeds via direct elimination of ammonia from an α-hydroxyalkyl radical or its conjugate base (i.

Exploring Temporal and Intensity Effects of Resistance Exercise on Inhibition: A Four-Arm Crossover Randomized Controlled Trial.

Objective: Given the recognized benefits of resistance exercise on both physical and cognitive domains, elucidating how to maximize its benefit is pivotal. This study aims to evaluate these effects in terms of their timing and intensity on cognitive performance.

Methods: This was a four-arm, crossover randomized controlled trial.

Complete Reconstitution of the Apramycin Biosynthetic Pathway Demonstrates the Unusual Incorporation of a β-d-Sugar Nucleotide in the Final Glycosylation Step.

Apramycin is a widely used aminoglycoside antibiotic with applications in veterinary medicine. It is composed of a 4-amino-4-deoxy-d-glucose moiety and the pseudodisaccharide aprosamine, which is an adduct of 2-deoxystreptamine and an unusual eight-carbon bicyclic dialdose. Despite its extensive study and relevance to medical practice, the biosynthetic pathway of this complex aminoglycoside nevertheless remains incomplete.

Effects of resistance exercises on inhibitory control and plasma epinephrine levels: A registered report of a crossover randomized controlled trial.

According to the locus coeruleus-norepinephrine (LC-NE) theory, activity of the LC, the major releaser of NE in the brain, regulates inhibitory control. As there is reciprocal communication between circulating epinephrine and the LC, plasma epinephrine is used as the index of LC-NE activity. The aim of this crossover randomized controlled trial is to expand on previous findings by investigating the effects of free-weight, multiple-joint, and structural barbell resistance exercises.

Reconstitution of the Final Steps in the Biosynthesis of Valanimycin Reveals the Origin of Its Characteristic Azoxy Moiety.

Valanimycin is an azoxy-containing natural product isolated from the fermentation broth of Streptomyces viridifaciens MG456-hF10. While the biosynthesis of valanimycin has been partially characterized, how the azoxy group is constructed remains obscure. Herein, the membrane protein VlmO and the putative hydrazine synthetase ForJ from the formycin biosynthetic pathway are demonstrated to catalyze N-N bond formation converting O-(l-seryl)-isobutyl hydroxylamine into N-(isobutylamino)-l-serine.

Biosynthetic Origin of the Octose Core and Its Mechanism of Assembly during Apramycin Biosynthesis.

Apramycin is an aminoglycoside antibiotic isolated from and that has found clinical use in veterinary medicine. The apramycin structure is notable for its atypical eight-carbon bicyclic dialdose (octose) moiety. While the apramycin biosynthetic gene cluster () has been identified and several of the encoded genes functionally characterized, how the octose core itself is assembled has remained elusive.

Effects of green tea-derived natural products on resistance exercise training in sarcopenia: A retrospective narrative mini-review.

Skeletal muscle function deficits result in metabolic disease development and physical dysfunction in older adults. Sarcopenia is characterized by a decrease in muscle mass and strength with advancing age, and it increases the risks of mobility impairments, disease development, and mortality. Lifestyle interventions involving a combination of diet and exercise to prevent and attenuate sarcopenia warrant substantial research attention.

-Adenosylmethionine: more than just a methyl donor.

Covering: from 2000 up to the very early part of 2023-Adenosyl-L-methionine (SAM) is a naturally occurring trialkyl sulfonium molecule that is typically associated with biological methyltransfer reactions. However, SAM is also known to donate methylene, aminocarboxypropyl, adenosyl and amino moieties during natural product biosynthetic reactions. The reaction scope is further expanded as SAM itself can be modified prior to the group transfer such that a SAM-derived carboxymethyl or aminopropyl moiety can also be transferred.

Changing Fates of the Substrate Radicals Generated in the Active Sites of the B-Dependent Radical SAM Enzymes OxsB and AlsB.

OxsB is a B-dependent radical SAM enzyme that catalyzes the oxidative ring contraction of 2'-deoxyadenosine 5'-phosphate to the dehydrogenated, oxetane containing precursor of oxetanocin A phosphate. AlsB is a homologue of OxsB that participates in a similar reaction during the biosynthesis of albucidin. Herein, OxsB and AlsB are shown to also catalyze radical mediated, stereoselective C2'-methylation of 2'-deoxyadenosine monophosphate.

Effects of acute resistance exercise with different loads on appetite, appetite hormones and autonomic nervous system responses in healthy young men.

Although the effect of continuous aerobic exercise on the appetite has been widely explored, the influence of resistance exercise (RE) with different variables, including training loads, training volume, and inter-set rest, on appetite responses requires further investigation. This study examined the importance of training load in RE-induced appetite regulation, with the total training volume and inter-set rest equalized. In total, 11 healthy young men (age = 23 ± 2 years, body mass index = 22 ± 2 kg/m) were included.

Supervised high-load resistance training for improving muscle strength and quality in prediabetic older adults: A pilot randomized controlled trial.

Objective: To investigate the effects of high- and low-load supervised, volume-matched resistance training (RT) on body composition, muscle function, and functional capacity in older adults with prediabetes.

Methods: Older adults with prediabetes were recruited and randomly assigned to high-load RT (n = 13), low-load RT (n = 12), or control groups (n = 12).

Results: No significant differences were observed in body composition at postintervention.

Two Radical SAM Enzymes Are Necessary and Sufficient for the In Vitro Production of the Oxetane Nucleoside Antiviral Agent Albucidin.

Oxetanocin A and albucidin are two oxetane natural products. While the biosynthesis of oxetanocin A has been described, less is known about albucidin. In this work, the albucidin biosynthetic gene cluster is identified in Streptomyces.

Deciphering the Reaction Pathway of Mononuclear Iron Enzyme-Catalyzed N≡C Triple Bond Formation in Isocyanide Lipopeptide and Polyketide Biosynthesis.

Despite the diversity of reactions catalyzed by 2-oxoglutarate-dependent nonheme iron (Fe/2OG) enzymes identified in recent years, only a limited number of these enzymes have been investigated in mechanistic detail. In particular, several Fe/2OG-dependent enzymes capable of catalyzing isocyanide formation have been reported. While the glycine moiety has been identified as a biosynthon for the isocyanide group, how the actual conversion is effected remains obscure.

Flavin-enabled reductive and oxidative epoxide ring opening reactions.

Epoxide ring opening reactions are common and important in both biological processes and synthetic applications and can be catalyzed in a non-redox manner by epoxide hydrolases or reductively by oxidoreductases. Here we report that fluostatins (FSTs), a family of atypical angucyclines with a benzofluorene core, can undergo nonenzyme-catalyzed epoxide ring opening reactions in the presence of flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NADH). The 2,3-epoxide ring in FST C is shown to open reductively via a putative enol intermediate, or oxidatively via a peroxylated intermediate with molecular oxygen as the oxidant.

Identification of the Early Steps in Herbicidin Biosynthesis Reveals an Atypical Mechanism of -Glycosylation.

Herbicidins are adenosine-derived nucleoside antibiotics with an unusual tricyclic core structure. Deletion of the genes responsible for formation of the tricyclic skeleton in sp. L-9-10 reveals the o importance of Her4, Her5, and Her6 in the early stages of herbicidin biosynthesis.

DDX18 prevents R-loop-induced DNA damage and genome instability via PARP-1.

R loops occur frequently in genomes and contribute to fundamental biological processes at multiple levels. Consequently, understanding the molecular and cellular biology of R loops has become an emerging area of research. Here, it is shown that poly(ADP-ribose) polymerase-1 (PARP-1) can mediate the association of DDX18, a putative RNA helicase, with R loops thereby modulating R-loop homeostasis in endogenous R-loop-prone and DNA lesion regions.

Characterization of the Oxazinomycin Biosynthetic Pathway Revealing the Key Role of a Nonheme Iron-Dependent Mono-oxygenase.

Oxazinomycin is a -nucleoside natural product with antibacterial and antitumor activities. In addition to the characteristic -glycosidic linkage shared with other -nucleosides, oxazinomycin also features a structurally unusual 1,3-oxazine moiety, the biosynthesis of which had previously been unknown. Herein, complete in vitro reconstitution of the oxazinomycin biosynthetic pathway is described.

Byproduct formation during the biosynthesis of spinosyn A and evidence for an enzymatic interplay to prevent its formation.

Biosynthesis of spinosyn A in involves a 1,4-dehydration followed by an intramolecular [4 + 2]-cycloaddition catalyzed by SpnM and SpnF, respectively. The cycloaddition also takes place in the absence of SpnF leading to questions regarding its mechanism of catalysis and biosynthetic role. Substrate analogs were prepared with an unactivated dienophile or an acyclic structure and found to be unreactive consistent with the importance of these features for cyclization.

Studies of GenK and OxsB, two B-dependent radical SAM enzymes involved in natural product biosynthesis.

The B-dependent radical SAM enzymes are an emerging subgroup of biological catalysts that bind a cobalamin cofactor in addition to the canonical [FeS] cluster characteristic of radical SAM enzymes. Most of the B-dependent radical SAM enzymes that have been characterized mediated methyltransfer reactions; however, a small number are known to catalyze more diverse reactions such as ring contractions. Thus, Genk is a methyltransferase from the gentamicin C biosynthetic pathway, whereas OxsB catalyzes the oxidative ring contraction of 2'-deoxyadenosine 5'-phosphates to generate an oxetane aldehyde during the biosynthesis of oxetanocin A.