Enzymatic Transfer Research Articles

Emerging roles of mitochondrial sirtuin SIRT5 in succinylation modification and cancer development

Succinylation represents an emerging class of post-translational modifications (PTMs), characterized by the enzymatic or non-enzymatic transfer of a negatively charged four-carbon succinyl group to the ϵ-amino group of lysine residues, mediated by succinyl-coenzyme A. Recent studies have highlighted the involvement of succinylation in various diseases, particularly cancer progression. Sirtuin 5 (SIRT5), a member of the sirtuin family, has been extensively studied for its robust desuccinylase activity, alongside its deacetylase function. To date, only a limited number of SIRT5 substrates have been identified. These substrates mediate diverse physiological processes such as glucose oxidation, fatty acid oxidation, ammonia detoxification, reactive oxygen species scavenging, anti-apoptosis, and inflammatory responses. The regulation of these activities can occur through either the same enzymatic activity acting on different substrates or distinct enzymatic activities targeting the same substrate. Aberrant expression of SIRT5 has been closely linked to tumorigenesis and disease progression; however, its role remains controversial. SIRT5 exhibits dual functionalities: it can promote tumor proliferation, metastasis, drug resistance, and metabolic reprogramming, thereby acting as an oncogene; conversely, it can also inhibit tumor cell growth and induce apoptosis, functioning as a tumor suppressor gene. This review aims to provide a comprehensive overview of the current research status of SIRT5. We discuss its structural characteristics and regulatory mechanisms, compare its functions with other sirtuin family members, and elucidate the mechanisms regulating SIRT5 activity. Specifically, we focus on the role of succinylation modification mediated by SIRT5 in tumor progression, highlighting how desuccinylation by SIRT5 modulates tumor development and delineating the underlying mechanisms involved.

Association between ABCB4 variants and intrahepatic cholestasis of pregnancy

The ABCB4 gene encodes multidrug resistance protein 3(MDR3), which is a phosphatidylcholine(PC) transfer enzyme that transfers lecithin from the inner part of the phospholipid bilayer to the extracellular bile. The occurrence of intrahepatic cholestasis of pregnancy(ICP) is closely related to ABCB4 variants, but there is limited research on this topic in southern Anhui, China. We sequenced ABCB4 in pregnant women with ICP and healthy pregnant women to explore the relationship. A total of 30 patients diagnosed with ICP were selected as the study objects and 90 healthy pregnant women were selected as the control group. DNA was extracted from peripheral blood of ICP patients and healthy pregnant women, 27 exons were sequencing by Sanger sequencing. Polymerase chain reaction (PCR) was used to amplify those exons. PolyPhen2, Mutation Taster, Provean, SIFT and Mutpred2 were used to predict protein structure, and Pymol software was used to predict the impact of missense variant c.1954 A > G(p.Arg652Gly) on proteins. Four exonic variants of ABCB4 gene were detected in ICP patients and healthy pregnant women, including synonymous variants c.175 C > T, c.504 C > T,c.711 A > T and missense variant c.1954 A > G(p.Arg652Gly). The incidence of the missense variant c.1954 A > G(p.Arg652Gly) was 6/90 in healthy pregnant womenand 8/30 in ICP patients.In healthy pregnant women with the missense variant c.1954 A > G(p.Arg652Gly), no other exonic variants were found. In ICP patients with missense variant c.1954 A > G(p.Arg652Gly), other exonic variants were found. PolyPhen2, Mutation Taster, Provean, SIFT and Mutpred2 were used to predict that the four exonic variants were benign, while Pymol was used to showed that the missense variant was located in the linker region of MDR3 and had a slight impact on protein function. Among ICP patients with missense variant c.1954 A > G(p.Arg652Gly), patients with three exonic variants(c.504 C > T, c.711 A > T, c.1954 A > G) had higher γ-GT, TBA, ALT and AST than those with two exonic variants. ABCB4 missense variant c.1954 A > G(p.Arg652Gly) requires the combination of other variants(c.175 C > T, c.504 C > T,c.711 A > T) to cause ICP symptoms, and when combined with other variants, it has a superimposed effect.

The development and application of an engineered direct electron transfer enzyme for continuous levodopa monitoring

Levodopa, the primary treatment for Parkinson’s Disease, has a narrow therapeutic window further complicated by the lack of real-time feedback, primarily due to the absence of an enzyme specific to levodopa. We addressed this by developing a novel direct electron transfer type (DET) enzyme, copper dehydrogenase (CoDH), engineered from an extremophile derived multicopper oxidase (MCO), for use in a continuous levodopa sensor. By introducing mutations into the type 2 and type 3 copper ligand histidine residues, the enzyme drastically decreased its oxidase activity while enhancing DET activity with the electrode. Using this developed CoDH, a chronoamperometric levodopa sensor was constructed, which was minimally affected by environmental changes, or by interferents, including levodopa metabolites, adjunct medications, and common plasma and interstitial fluid components. A miniaturized levodopa sensor was constructed and was able to detect levodopa as low as 138 nM, suggesting its future application for in vivo subcutaneous measurement.

Construction of a Novel Stable Electron Transfer Protein for the Creation of Artificial Direct Electron Transfer Enzymes

In recent years, wearable sensors aiming to enable continuous measurement for disease prevention and diagnosis have been the focus of much research. Wearable sensors are often used inside the user's body or on biological surfaces. To reduce the burden on the user, these devices must be safe and compact. Lithium has been used as the conventional power source, but lithium batteries are not biocompatible and are not safe. Therefore, biofuel cells (BFCs) that use enzymes as electrodes are expected as a power source. In conventional BFCs, mediated electron transfer (MET) -type enzymes, in which a low molecular weight redox substance (mediator) mediates the electron transfer between the electrode and the enzyme, have been the mainstream. However, the low long-term stability and toxicity of the mediator used has been a challenge. Direct electron transfer (DET) -type enzymes, which do not require a mediator for electron transfer between the electrode and enzyme, are therefore attracting attention. However, there are few reports on DET-type enzymes, and research is being conducted to convert existing MET-type enzymes to DET-type enzymes. Most of the currently reported artificial DET-type enzymes have heme proteins as electron transfer subunits. However, heme proteins have low long-term stability. In the present study, we focused on the electron transfer domain of multicopper oxidase (McoP) from hyperthermophilic archaeon, Pyrobaculum aerophilum, which has excellent long-term stability. McoP has four copper atoms, which can be divided into three types according to their spectroscopic and magnetic properties. Type 1 (T1) Cu makes the enzyme blue and shows strong optical absorption at a wavelength of 610 nm due to d-d transition. Type 2 (T2) Cu is colorless and can be detected by electro paramagnetic resonance spectroscopy (EPR). The T3 type is distinguished by an optical absorption band at a wavelength of 330 nm. T1Cu has a copper atom bonded to two histidine residues and one cysteine, forming a distorted triangular pyramidal structure. T1Cu in McoP also has one methionine axially present, which affects the redox potential of the enzyme and stabilizes it. T1Cu and all ligands are present in domain 3. Therefore, we hypothesized that domain 3 alone could function as an electron-transfer subunit with excellent long-term stability.ExperimentPlasmid vector for expression of domain 3 of McoP was prepared from McoP expression vector using In-Fusion clonig. Subsequently, the protein was expressed in E. coli BL21-Codon Plus (DE3) RIPL. The purified protein was then evaluated and confirmed. Spectroscopic observation showed a peak around 600 nm derived from T1Cu as well as McoP. Cyclic voltammetry (CV) was performed for electrochemical evaluation of domain 3. The prified protein (1 mg/ml) was modified onto a gold electrode by physisorption. Domain 3 modified electrode was used as working electrode. CVs were performed in a three-electrode system using a platinum counter electrode and an Ag/AgCl reference electrode. The CV perfprmed under O2 or N2 saturated condition. The domain 3 modified electrode showed redox peaks. These results indicate that domain 3 can be expressed and functions as an electron transfer subunit. In the future, the present protein will be used as an electron transfar subunit to convert MET-type enzymes to DET-type enzymes. Figure 1

Investigating the Core Structure of Reuteran with High-Content Linear (α1 → 6) Linkages Synthesized by Limosilactobacillus mucosae L24-B GtfB-Type Glucanotransferase.

Reuteran is a functional homopolysaccharide comprising major (α1 → 4) and interspersed (α1 → 6) linkages whose properties and functions are directly associated with the structure. In order to enrich the structural variety and application prospects of reuteran, a GtfB-type 4,6-α-glucanotransferase from Limosilactobacillus mucosae L24-B (LmGtfB), which can synthesize reuteran with high-content linear (α1 → 6) linkages, was screened. LmGtfB exhibited 4,6-α-glucanotransferase activity against starch or dextrin and can synthesize both linear and branching (α1 → 6) linkages, which offered advantages in terms of source and cost. The as-produced reuteran had the highest content of linear (α1 → 6) linkages (19% in the methylation result) among the reuterans synthesized by other GtfB-type 4,6-α-glucanotransferases. A purification method was established and applied to the extraction of the core structure of the LmGtfB products. 1H NMR and enzymatic hydrolysis revealed that the core structure contains 46.24% (α1 → 6) linkages and alternating (α1 → 4)/(α1 → 6) linkages, which was formed by enzymatic transfer of maltose.

Aluminum Fluorides as Noncovalent Lewis Acids in Proteins: The Case of Phosphoryl Transfer Enzymes.

The Protein Data Bank (PDB) was scrutinized for the presence of noncovalent O ⋅ ⋅ ⋅ Al Triel Bonding (TrB) interactions, involving protein residues (e. g. GLU and GLN), adenosine/guanine diphosphate moieties (ADP and GDP), water molecules and two aluminum fluorides (AlF3 and AlF4 -). The results were statistically analyzed, revealing a vast number of O ⋅ ⋅ ⋅ Al contacts in the active sites of phosphoryl transfer enzymes, with a marked directionality towards the Al σ-/π-hole. The physical nature of the TrBs studied herein was analyzed using Molecular Electrostatic Potential (MEP) maps, the Quantum Theory of Atoms in Molecules (QTAIM), the Non Covalent Interaction plot (NCIplot) visual index and Natural Bonding Orbital (NBO) studies. As far as our knowledge extends, it is the first time that O ⋅ ⋅ ⋅ Al TrBs are analyzed within a biological context, participating in protein trapping mechanisms related to phosphoryl transfer enzymes. Moreover, since they are involved in the stabilization of aluminum fluorides inside the protein's active site, we believe the results reported herein will be valuable for those scientists working in supramolecular chemistry, catalysis and rational drug design.

Radical-mediated regiodivergent C(sp3)–H functionalization of N-substituted indolines via enzymatic carbene transfer

Radical-mediated regiodivergent C(sp3)–H functionalization of N-substituted indolines via enzymatic carbene transfer

Cu2O-Mediated Heterojunction Conversion from Dual Type II to Dual Z-Scheme: Its Application in Photoelectric-Colorimetric Dual-Mode Detection of Fat Mass and Obesity-Associated (FTO) Protein.

Although the construction of heterojunction has been used in photoelectrochemical (PEC) biosensors, their potential for tunable optical properties has not been deeply explored. Based on the fact that a type-II heterojunction and Z-scheme heterojunction have the same energy band structure, effective alteration of the electron transfer pathway has been achieved by introducing unique photoactive materials into the system and exploiting the interactions between the photomaterials. Based on this, we reported a novel polarity-switchable dual-mode sensor for fat mass and obesity-associated (FTO) protein analysis. Specifically, the MgIn2S4/Bi2MoO6/Bi2S3 dual type-II heterojunction was used as the sensing interface in concert with the rolling circle amplification, CRISPR/Cas12, and terminal DNA transfer enzyme multiamplification strategies, and finally, Cu2O was captured at the sensing interface. Due to the matched energy band, the introduction of Cu2O effectively changed the electron transfer pathway and realized the conversion from a dual type-II heterojunction to a dual Z-scheme heterojunction. It caused the switch of the photocurrent from the anode to the cathode. The developed PEC method showed high sensitivity and selectivity for FTO protein detection in the range of 0.0005-500 μg/L. In addition, based on the peroxidase-like activity of Cu2O to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine by H2O2, the electrode system also achieved the colorimetric detection of FTO protein using the naked eye with the change of the color of the detection solution from colorless to blue. The detection range was from 0.05 to 500 μg/L. This work developed a photoelectrochemical-colorimetric biosensing platform with consciously designed semiconductor structures, revealing the potential of semiconductor-structured transformations in future sensing fields.

Sulfamethoxazole degradation in tri-electrode microbial electrochemical systems: Metabolomic and Metagenomic insights into organic pollution effects

Organic pollutants can alter the physicochemical properties and microbial communities of water bodies. In water contaminated with organic pollutants, the unique extracellular electron transfer mechanisms that promote sulfamethoxazole (SMX) degradation in tri-electrode microbial electrochemical systems (TE-MES) may be impacted. To simulate biodegradable organic matter contamination, glucose (GLU) was added. Metagenomics and metabolomics were used to analyze changes in microbial community structure, metabolism, and function on the electrodes. GLU addition accelerated water quality deterioration, and enhanced SMX degradation. Microbial taxa on the electrodes experienced selective enrichment. Notably, methanogens and SMX-degrading bacteria were enriched, while denitrifying bacteria and antibiotic-resistant bacteria were suppressed. Enriched metabolites were linked to 15 metabolic pathways and other functions like microbial signaling and genetics. Non-redundant genes also clustered in metabolic pathways, aligning with metabolite enrichment results. Additional pathways involved life cycle processes and protein interactions. Enzymes related to carbon metabolism, particularly glycoside hydrolases, increased significantly, indicating a shift in carbon metabolism on microbial electrodes after GLU addition. The abundance of intracellular electron transfer enzymes rose, while outer membrane proteins decreased. This contrasts with the typical TE-MES mechanism where outer membrane proteins facilitate SMX degradation. The presence of organic pollution may shift SMX degradation from an extracellular electrochemical process to an intracellular metabolic process, possibly involving co-metabolism with simple organic compounds. This study provides mechanistic insights and theoretical guidance for using TE-MES with embedded microbial electrodes to treat antibiotic-contaminated water affected by organic pollution.

Metal fluorides—multi-functional tools for the study of phosphoryl transfer enzymes, a practical guide

Enzymes facilitating the transfer of phosphate groups constitute the most extensive protein families across all kingdoms of life. They make up approximately 10% of the proteins found in the human genome. Understanding the mechanisms by which enzymes catalyze these reactions is essential in characterizing the processes they regulate. Metal fluorides can be used as multifunctional tools to study these enzymes. These ionic species bear the same charge as phosphate and the transferring phosphoryl group and, in addition, allow the enzyme to be trapped in catalytically important states with spectroscopically sensitive atoms interacting directly with active site residues. The ionic nature of these phosphate surrogates also allows their removal and replacement with other analogs. Here, we describe the best practices to obtain these complexes, their use in NMR, X-ray crystallography, cryo-EM, and SAXS and describe a new metal fluoride, scandium tetrafluoride, which has significant anomalous signal using soft X-rays.

Introducing enzymatic cleavage features and transfer learning realizes accurate peptide half-life prediction across species and organs.

Peptide drugs are becoming star drug agents with high efficiency and selectivity which open up new therapeutic avenues for various diseases. However, the sensitivity to hydrolase and the relatively short half-life have severely hindered their development. In this study, a new generation artificial intelligence-based system for accurate prediction of peptide half-life was proposed, which realized the half-life prediction of both natural and modified peptides and successfully bridged the evaluation possibility between two important species (human, mouse) and two organs (blood, intestine). To achieve this, enzymatic cleavage descriptors were integrated with traditional peptide descriptors to construct a better representation. Then, robust models with accurate performance were established by comparing traditional machine learning and transfer learning, systematically. Results indicated that enzymatic cleavage features could certainly enhance model performance. The deep learning model integrating transfer learning significantly improved predictive accuracy, achieving remarkable R2 values: 0.84 for natural peptides and 0.90 for modified peptides in human blood, 0.984 for natural peptides and 0.93 for modified peptides in mouse blood, and 0.94 for modified peptides in mouse intestine on the test set, respectively. These models not only successfully composed the above-mentioned system but also improved by approximately 15% in terms of correlation compared to related works. This study is expected to provide powerful solutions for peptide half-life evaluation and boost peptide drug development.

Diverse avenues of research support the transmethylation theory of psychosis: implications for neuroprotection

Transmethylation in the context of psychiatry has historically referred to the enzymatic transfer of a methyl group from one biochemical to another, whose resulting function can change so dramatically that a biochemical like tryptamine, for example, is converted into the hallucinogen dimethyltryptamine. Central to endogenous methylation activity is the folate cycle, which generates the primary transferable methyl groups in mammalian biochemistry. The relevance of this cycle to mental health becomes clear when the cycle is dysregulated, often leading to a buildup of both homocysteine and S-adenosylhomocysteine (SAH), while accompanied by a transient reduction in the intended physiologic target, S-adenosylmethionine (SAM). This paper includes an in-depth review of the causes of folate cycle perturbations associated with psychotic symptoms, expounding on alternative downstream pathways which are activated and pointing toward potential etiologic agents of the associated psychosis, the methylated tertiary amines N-methyl-salsolinol, N-methyl-norsalsolinol, and adrenochrome, which appear in scientific reports concerning their association with hallucinogenic and/or neurotoxic outcomes. Electrotopological state (E-state) data has been generated for these compounds, illustrating a strong similarity with hallucinogens, particularly in terms of the E-state of the nitrogen in their tertiary amine moieties. In light of the role the folate cycle plays in transmethylation, neuroprotective strategies to prevent the transition to psychosis are suggested, including the advisory that folate supplementation can be harmful depending on the status of other relevant biochemicals.

Investigating the Anti-adipogenic Potential of Xanthium strumarium Linn. Leaves Fractions: HPTLC-MS Characterization, Enzymatic Analysis, and 3T3-L1 Adipocyte Differentiation Assay in Oxidative Stress-modulated Adipogenesis Cascade

Background Molecular pathogenesis of obesity is initiated by cellular oxidative stress along with increased adipogenesis. For the search of better alternatives of synthetic molecules in terms of their adverse events, naturally, existing compounds are now a research focus. In this context, Xanthium strumarium ( X. strumarium) Linn. exhibited anti-diabetic activities and proved to have efficacy in neutralizing very near pathological targets to obesity. Purpose This study is aimed toward bioactivity-guided fraction isolation of methanolic leaves extract, where bioactivity refers to anti-adipogenesis and anti-oxidant efficacy in in vitro enzymatic and three-day transfer, inoculum 3×105 cells (3T3-L1) adipocyte differentiation assay. Materials and Methods Collection and drying of the raw leaves followed by cold extraction in methanol and flash chromatography for bioactive fraction isolation. 3T3-L1 cell line was utilized for adipocyte differentiation assay of those and on the other hand in vitro pancreatic lipase, α-glucosidase, and α-amylase enzymatic assays were analyzed. Based on exhibited activities, selected fractions are further characterized by high-performance thin-layer chromatography-mass spectrometry (HPTLC-MS). Results The most active fractions from these assays underwent characterization via HPTLC-MS. Fractions 2 and 3 exhibited potent activities in all enzymatic assays (α-glucosidase IC50: 2.48 ± 0.015, 2.84 ± 0.030 µg/mL; α-amylase IC50: 1.98 ± 0.050, 1.79 ± 0.045 µg/mL; pancreatic lipase IC50: 3.16 ± 0.030, 3.18 ± 0.040 µg/mL) and displayed significant inhibition of adipocyte differentiation in 3T3-L1 cell line. These fractions further identified through HPTLC-MS, contained compounds like β-sitosterol and quercetin, affirming their potential bioactivity. Conclusion The study underscores the potential of X. strumarium Linn. fractions as promising natural alternatives for combating obesity-related pathways, highlighting their significance in developing future anti-obesity therapeutics.

Enzymatic radical fluorine transfer

Enzymatic radical fluorine transfer

Abstract SY11-02: Small molecule inhibitors of RNA modifying enzymes as precision cancer therapeutics

Abstract Over 100 modifications to RNA are known to occur in human cells, where they influence many aspects of RNA biology, including protein and nucleic acid interactions. Our survey of human RNA-modifying enzymes with selectively essential phenotypes in specific cancers, suggests that these cancer-essential enzymes fall into four mechanistic categories: group transfer enzymes; base editors; nucleases; and helicases. Our team has discovered nanomolar or picomolar inhibitors of cancer-essential enzymes within each of these four categories. DHX9, a novel cancer target, is a multifunctional DEAH-box RNA helicase which can unwind regions of double-stranded DNA and RNA helices but has a greater propensity for secondary structures such as DNA/RNA hybrids (R-loops), circular RNA and DNA/RNA G-quadruplexes. DHX9 interacts with and regulate a large variety of proteins, including key proteins in DNA damage repair pathways such as BRCA1, ATR, Ku86, and WRN. We previously demonstrated that DHX9 inhibition is selectively efficacious in microsatellite high (MSI-H)/defective mismatch repair (dMMR) tumor models, in vitro and in vivo. Further profiling of DHX9 inhibitors across a broad panel of cancer cell lines reveals that tumor cells with Loss-of-Function (LOF) mutations in the DNA damage repair genes BRCA1 and/or BRCA2 (as defined by somatic mutations including single-nucleotide variants and/or copy number loss), are also selectively responsive to DHX9 inhibitor treatment. Selective dependence on DHX9 was observed in both ovarian and breast cancer cell lines that exhibit BRCA1 and/or BRCA2 LOF. DHX9 inhibition leads to increased RNA/DNA secondary structures such as R-loops and G-quadruplexes, resulting in subsequent DNA damage and increased replication stress. Cell lines that exhibit BRCA1 and/or BRCA2 LOF appear unable to resolve this replication stress and showed S-G2 phase cell cycle arrest prior to onset of apoptosis. An orally bioavailable DHX9 inhibitor was dosed in vivo to assess DHX9 dependency within multiple human xenografts representing triple negative breast cancer and high-grade serous ovarian cancer with BRCA1 and/or BRCA2 LOF. In all models, DHX9 inhibition was well tolerated for a period of up to 28 days, with robust and significant tumor growth inhibition - including tumor regression - observed in multiple BRCA1 and/or BRCA2 LOF models; in contrast, minimal tumor growth inhibition was observed in BRCA1 and BRCA2 wild type models. These results portend DHX9 inhibition as a novel treatment modality for patients with BRCA1 and/or BRCA2 LOF across multiple tumor types, including breast and ovarian cancer. Citation Format: Robert A. Copeland, Jennifer Castro, Matthew H. Daniels, Deepali Gotur, Young-Tae Lee, Shihua Yao, David Brennan, Brian T. Johnston, Monique Laidlaw, Sunaina Pai, Jie Wu, Rishabh Bansal, Anugraha Raman, Shane M. Buker, Julie Liu, E. Allen Sickmier, Kevin Knockenhauer, Chuang Lu, Stephen J. Blakemore, Serena J. Silver, P. Ann Boriack-Sjodin, Kenneth W. Duncan, Jason A. Sager. Small molecule inhibitors of RNA modifying enzymes as precision cancer therapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr SY11-02.

Universal recording of immune cell interactions in vivo.

Immune cells rely on transient physical interactions with other immune and non-immune populations to regulate their function1. To study these 'kiss-and-run' interactions directly in vivo, we previously developed LIPSTIC (labelling immune partnerships by SorTagging intercellular contacts)2, an approach that uses enzymatic transfer of a labelled substrate between the molecular partners CD40L and CD40 to label interacting cells. Reliance on this pathway limited the use of LIPSTIC to measuring interactions between CD4+ T helper cells and antigen-presenting cells, however. Here we report the development of a universal version of LIPSTIC (uLIPSTIC), which can record physical interactions both among immune cells and between immune and non-immune populations irrespective of the receptors and ligands involved. We show that uLIPSTIC can be used, among other things, to monitor the priming of CD8+ T cells by dendritic cells, reveal the steady-state cellular partners of regulatory T cells and identify germinal centre-resident T follicular helper cells on the basis of their ability to interact cognately with germinal centre B cells. By coupling uLIPSTIC with single-cell transcriptomics, we build a catalogue of the immune populations that physically interact with intestinal epithelial cells at the steady state and profile the evolution of the interactome of lymphocytic choriomeningitis virus-specific CD8+ T cells in multiple organs following systemic infection. Thus, uLIPSTIC provides a broadly useful technology for measuring and understanding cell-cell interactions across multiple biological systems.

Heavy water inhibits DNA double-strand break repairs and disturbs cellular transcription, presumably via quantum-level mechanisms of kinetic isotope effects on hydrolytic enzyme reactions.

Heavy water, containing the heavy hydrogen isotope, is toxic to cells, although the underlying mechanism remains incompletely understood. In addition, certain enzymatic proton transfer reactions exhibit kinetic isotope effects attributed to hydrogen isotopes and their temperature dependencies, indicative of quantum tunneling phenomena. However, the correlation between the biological effects of heavy water and the kinetic isotope effects mediated by hydrogen isotopes remains elusive. In this study, we elucidated the kinetic isotope effects arising from hydrogen isotopes of water and their temperature dependencies in vitro, focusing on deacetylation, DNA cleavage, and protein cleavage, which are crucial enzymatic reactions mediated by hydrolysis. Intriguingly, the intracellular isotope effects of heavy water, related to the in vitro kinetic isotope effects, significantly impeded multiple DNA double-strand break repair mechanisms crucial for cell survival. Additionally, heavy water exposure enhanced histone acetylation and associated transcriptional activation in cells, consistent with the in vitro kinetic isotope effects observed in histone deacetylation reactions. Moreover, as observed for the in vitro kinetic isotope effects, the cytotoxic effect on cell proliferation induced by heavy water exhibited temperature-dependency. These findings reveal the substantial impact of heavy water-induced isotope effects on cellular functions governed by hydrolytic enzymatic reactions, potentially mediated by quantum-level mechanisms underlying kinetic isotope effects.

Enzymatic and non-enzymatic transnitrosylation: “SCAN”ning the SNO-proteome

In a recent study in Cell, Zhou etal.1 propose enzymatic transfer of nitric-oxide (NO)-related species from SNO-CoA to target proteins involved in insulin signaling; this function comprises an SNO-CoA-Assisted Nitrosylase (SCAN).

Bacterial Isothiocyanate Biosynthesis by Rhodanese-Catalyzed Sulfur Transfer onto Isonitriles.

Natural products bearing isothiocyanate (ITC) groups are an important group of specialized metabolites that play various roles in health, nutrition, and ecology. Whereas ITC biosynthesis via glucosinolates in plants has been studied in detail, there is a gap in understanding the bacterial route to specialized metabolites with such reactive heterocumulene groups, as in the antifungal sinapigladioside from Burkholderia gladioli. Here we propose an alternative ITC pathway by enzymatic sulfur transfer onto isonitriles catalyzed by rhodanese-like enzymes (thiosulfate:cyanide sulfurtransferases). Mining the B. gladioli genome revealed six candidate genes (rhdA-F), which were individually expressed in E. coli. By means of a synthetic probe, the gene products were evaluated for their ability to produce the key ITC intermediate in the sinapigladioside pathway. In vitro biotransformation assays identified RhdE, a prototype single-domain rhodanese, as the most potent ITC synthase. Interestingly, while RhdE also efficiently transforms cyanide into thiocyanate, it shows high specificity for the natural pathway intermediate, indicating that the sinapigladioside pathway has recruited a ubiquitous detoxification enzyme for the formation of a bioactive specialized metabolite. These findings not only elucidate an elusive step in bacterial ITC biosynthesis but also reveal a new function of rhodanese-like enzymes in specialized metabolism.

Remote stereocontrol with azaarenes via enzymatic hydrogen atom transfer.

Strategies for achieving asymmetric catalysis with azaarenes have traditionally fallen short of accomplishing remote stereocontrol, which would greatly enhance accessibility to distinct azaarenes with remote chiral centres. The primary obstacle to achieving superior enantioselectivity for remote stereocontrol has been the inherent rigidity of the azaarene ring structure. Here we introduce an ene-reductase system capable of modulating the enantioselectivity of remote carbon-centred radicals on azaarenes through a mechanism of chiral hydrogen atom transfer. This photoenzymatic process effectively directs prochiral radical centres located more than six chemical bonds, or over 6 Å, from the nitrogen atom in azaarenes, thereby enabling the production of a broad array of azaarenes possessing a remote γ-stereocentre. Results from our integrated computational and experimental investigations underscore that the hydrogen bonding and steric effects of key amino acid residues are important for achieving such high stereoselectivities.