Studies of Isonitrile Synthases Help Elucidate the Mechanism of Isonitrile Installation.

Isonitrile functional group is abundant in natural products and associated with various biological properties. To date, two pathways are known for isonitrile group installation. One is catalyzed by mononuclear nonheme iron dependent isonitrilases in which the reaction mechanism involves consecutive desaturation and decarboxylation processes.

Provision of a Redox Donor to Oxy-Ferrous PrnB Is Required for Pyrrolnitrin Synthesis.

PrnB, a long-standing member of the recently reclassified heme-dependent aromatic oxygenase (HDAO) superfamily of histidine-ligated heme enzymes, catalyzes the conversion of 7-chloro-l-tryptophan (7-Cl-Trp) to monodechloroaminopyrrolnitrin (MCAP). This unique ring rearrangement is an essential step in the biosynthesis of the broad-spectrum antifungal pyrrolnitrin. The conversion of 7-Cl-Trp to MCAP by PrnB differs from other HDAOs, which typically affect the mono- or dioxygenation of aromatic substrates.

Multiple Catalytic Branch Points in the Mechanism of Pyrrolidine Formation During Kainoid Biosynthesis Leads to Diverse Reaction Outcomes.

The biosynthesis of neuroexcitatory kainoids requires radical-mediated cyclization of -isoprenylated derivatives of l-glutamate catalyzed by nonheme iron and 2-oxoglutarate-dependent enzymes. While KabC and DabC from species of red algae catalyze this reaction during the biosynthesis of kainic acid and domoic acid, respectively, KabC can also produce a bicyclic lactone as an alternative reaction product. Herein, the radical-mediated catalytic pathways of KabC and DabC with the substrate -dimethylallyl l-glutamate are fully mapped demonstrating as many as three different product determining steps and competing processes of hydroxylation, C-C bond formation, intramolecular nucleophilic addition, desaturation and C-C bond cleavage leading to four different products including kainic acid, a bicyclic lactone, a hydroxylated product and oxidative rearrangement concomitant with elimination of formaldehyde.

An Alternative Mechanism for C-C Desaturation Underscores a Dual-Controlled Mechanism for the Fate of Radical Intermediate in Iron(II)- and 2-(Oxo)glutarate-Dependent Oxygenase DfmD.

The C(sp)-C(sp) desaturation catalyzed by iron(II)- and 2-(oxo)glutarate-dependent(Fe/2OG) oxygenase is a key step in the biosynthesis and modification of natural products. Similar to other C-H functionalization processes, the reaction is initiated by the active Fe(IV)-oxo species, which abstracts a hydrogen atom from the C-H bond. However, Fe/2OG desaturase suppresses the thermodynamically favored OH-rebound process.

Discovery of Noncanonical Iron and 2-Oxoglutarate Dependent Enzymes Involved in C-C and C-N Bond Formation in Biosynthetic Pathways.

Iron and 2-oxoglutarate dependent (Fe/2OG) enzymes utilize an Fe=O species to catalyze the functionalization of otherwise chemically inert C-H bonds. In addition to the more familiar canonical reactions of hydroxylation and chlorination, they also catalyze several other types of reactions that contribute to the diversity and complexity of natural products. In the past decade, several new Fe/2OG enzymes that catalyze C-C and C-N bond formation have been reported in the biosynthesis of structurally complex natural products.

Beyond the β-α-β Fold: Characterization of a SnoaL Domain in the Tautomerase Superfamily.

Tautomerase superfamily (TSF) members are constructed from a single β-α-β unit or two consecutively joined β-α-β units, and most have a catalytic Pro1. This pattern prevails throughout the superfamily consisting of more than 11,000 members where homo- or heterohexamers are localized in the 4-oxalocrotonate tautomerase (4OT)-like subgroup and trimers are found in the other four subgroups except for a small subset of 4OT trimers, symmetric and asymmetric, that are found in the 4OT-like subgroup. During a sequence similarity network (SSN) update, a small cluster of sequences (117 sequences) was discovered in the 4OT-like subgroup that begins with Pro1.

Fast Rule-based NER in SpaCy for Chest Radiography Reports with CheXpert's 14 Categories.

Chest X-ray imaging is widely used in medical examinations, with 2 billion performed globally annually. Interpreting X-ray images is time-consuming, prompting the development of AI-assisted systems. Generating a large set of high-quality labeled images is crucial for training accurate and unbiased deep learning models.

Automated Basilar Artery Lumen Segmentation for High Resolution in Black Blood MRI.

The basilar artery (BA) arises from the convergence of intracranial vertebral arteries in close proximity to the medulla oblongata and pons. As the largest artery in the posterior circulation, BA is susceptible to atherosclerosis and inflammatory conditions, necessitating the assessment of lumen shape and wall thickness in basilar artery diseases. Our objective is to develop an automated image segmentation technique for detecting the lumen and wall boundaries in black blood MR vessel wall images of the BA.

Bioinformatic, structural, and biochemical analysis leads to the discovery of novel isonitrilases and decodes their substrate selectivity.

Bacterial species, such as , utilize isonitrile-containing peptides (INPs) for trace metal trafficking, , copper or zinc. Despite their importance, very few INP structures have been characterized to date. Reported INPs consist of a peptide backbone and β-isonitrile amide moieties.

Comparison of a Nonheme Iron Cyclopropanase with a Homologous Hydroxylase Reveals Mechanistic Features Associated with Distinct Reaction Outcomes.

Despite the diversity of reactions catalyzed by mononuclear iron and 2-oxoglutarate-dependent enzymes, the factors that lead to diverse reaction outcomes beyond canonical hydroxylation remain elusive. Cyclopropanation reactions are of particular interest not only due to the prevalence of cyclopropane moieties in pharmaceuticals but also due to the chemistry that allows cyclopropanation to outcompete oxygen rebound. HrmJ is one such cyclopropanase from the biosynthetic pathway of hormaomycin; however, a homologue is herein discovered that instead catalyzes -hydroxylation of the same nitro enolate substrate.

Cyclopropanation and aziridination catalyzed by non-heme iron and 2-oxoglutarate dependent enzymes.

Cyclopropane and azacyclopropane, also known as aziridine, moieties are found in natural products. These moieties serve as pivotal components that lead to a broad spectrum of biological activities. While diverse strategies involving various classes of enzymes are utilized to catalyze formation of these strained three-membered rings, how non-heme iron and 2-oxoglutarate (Fe/2OG) dependent enzymes enable regio- and stereo-selective C-C and C-N ring closure has only been reported very recently.

Spectroscopic and computational studies of a bifunctional iron- and 2-oxoglutarate dependent enzyme, AsqJ.

Iron and 2-oxoglutarate dependent (Fe/2OG) enzymes exhibit an exceedingly broad reaction repertoire. The most prevalent reactivity is hydroxylation, but many other reactivities have also been discovered in recent years, including halogenation, desaturation, epoxidation, endoperoxidation, epimerization, and cyclization. To fully explore the reaction mechanisms that support such a diverse reactivities in Fe/2OG enzyme, it is necessary to utilize a multi-faceted research methodology, consisting of molecular probe design and synthesis, in vitro enzyme assay development, enzyme kinetics, spectroscopy, protein crystallography, and theoretical calculations.

Exploring the key elements for the successful management of primary otolaryngologic clinics in Taiwan.

Aim: This study aims to investigate the key elements for successful operation and management of primary otolaryngologic clinics in Taiwan amidst a declining birth rate and increasing competition among clinics. It employs the Innovation Through Tradition (ITT) theory as a theoretical framework to develop an operational model for effective management strategies.

Methods: This research utilized the triangulation method to identify key elements crucial for the operation and management of primary otolaryngologic clinics.

Variation in biosynthesis and metal-binding properties of isonitrile-containing peptides produced by Mycobacteria versus Streptomyces.

A number of bacteria are known to produce isonitrile-containing peptides (INPs) that facilitate metal transport and are important for cell survival; however, considerable structural variation is observed among INPs depending on the producing organism. While non-heme iron 2-oxoglutarate dependent isonitrilases catalyze isonitrile formation, how the natural variation in INP structure is controlled and its implications for INP bioactivity remain open questions. Herein, total chemical synthesis is utilized with X-Ray crystallographic analysis of mycobacterial isonitrilases to provide a structural model of substrate specificity that explains the longer alkyl chains observed in mycobacterial versus Streptomyces INPs.

LDL Receptor-Related Protein 1B Polymorphisms Associated with Increased Risk of Lymph Node Metastasis in Oral Cancer Group with Diabetes Mellitus.

Oral cancer ranks fourth among malignancies among Taiwanese men and is the eighth most common cancer among men worldwide in terms of general diagnosis. The purpose of the current study was to investigate how low-density lipoprotein receptor-related protein 1B (LDL receptor related protein 1B; LRP1B) gene polymorphisms affect oral squamous cell carcinoma (OSCC) risk and progression in individuals with diabetes mellitus (DM). Three LRP1B single-nucleotide polymorphisms (SNPs), including rs10496915, rs431809, and rs6742944, were evaluated in 311 OSCC cases and 300 controls.

Poly-γ-glutamylation of biomolecules.

Poly-γ-glutamate tails are a distinctive feature of archaeal, bacterial, and eukaryotic cofactors, including the folates and F. Despite decades of research, key mechanistic questions remain as to how enzymes successively add glutamates to poly-γ-glutamate chains while maintaining cofactor specificity. Here, we show how poly-γ-glutamylation of folate and F by folylpolyglutamate synthases and γ-glutamyl ligases, non-homologous enzymes, occurs via processive addition of L-glutamate onto growing γ-glutamyl chain termini.

Roadmaps for Guiding Chest Computed Tomography Interpretation involving Pneumonia.

CT scanning of the chest is one the most important imaging modalities available for pulmonary disease diagnosis. Lung segmentation plays a crucial step in the pipeline of computer-aided analysis and diagnosis. As deep learning models have achieved human-level accuracy in semantic segmentation of anatomical structures, we propose to use trained deep learning models to predict both healthy and infectious areas in chest CT slices.

Excision of a Protein-Derived Amine for -Aminobenzoate Assembly by the Self-Sacrificial Heterobimetallic Protein CADD.

Chlamydia protein associating with death domains (CADD), the founding member of a recently discovered class of nonheme dimetal enzymes termed hemeoxygenase-like dimetaloxidases (HDOs), plays an indispensable role in pathogen survival. CADD orchestrates the biosynthesis of -aminobenzoic acid (ABA) for integration into folate via the self-sacrificial excision of a protein-derived tyrosine (Tyr27) and several additional processing steps, the nature and timing of which have yet to be fully clarified. Nuclear magnetic resonance (NMR) and proteomics approaches reveal the source and probable timing of amine installation by a neighboring lysine (Lys152).

Mechanistic Analysis of Stereodivergent Nitroalkane Cyclopropanation Catalyzed by Nonheme Iron Enzymes.

BelL and HrmJ are α-ketoglutarate-dependent nonheme iron enzymes that catalyze the oxidative cyclization of 6-nitronorleucine, resulting in the formation of two diastereomeric 3-(2-nitrocyclopropyl)alanine (Ncpa) products containing -cyclopropane rings with (1'2') and (1'2') configurations, respectively. Herein, we investigate the catalytic mechanism and stereodivergency of the cyclopropanases. The results suggest that the nitroalkane moiety of the substrate is first deprotonated to produce the nitronate form.

An S=1 Iron(IV) Intermediate Revealed in a Non-Heme Iron Enzyme-Catalyzed Oxidative C-S Bond Formation.

Ergothioneine (ESH) and ovothiol A (OSHA) are two natural thiol-histidine derivatives. ESH has been implicated as a longevity vitamin and OSHA inhibits the proliferation of hepatocarcinoma. The key biosynthetic step of ESH and OSHA in the aerobic pathways is the O -dependent C-S bond formation catalyzed by non-heme iron enzymes (e.