Natural Flavins:Occurrence, Role, and Noncanonical Chemistry

Flavoproteins are of key importance to all life on earth for both primary and secondary metabolism. Most flavin-dependent enzymes utilize flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD) as redox cofactor for single-electron and hydride transfer as well as oxidation and oxygenation chemistry at the C4a-locus. Over the last decades, several naturally occurring modified flavins, like 8-formylFAD, F420, and prenylFMN, and covalently bound flavins have been discovered, and were found to further expand the toolbox of flavin chemistry, showcasing extraordinary redox potentials and unprecedented chemistry. Recently, also several examples of “exotic” flavin chemistry, such as N5-oxygenation, have been identified in enzymes that utilize the standard flavins FMN and FAD. It shows that nature has been extremely inventive in exploiting flavins and flavin derivatives as cofactors for an exceptionally wide variety of reactions. Future research will reveal whether other, so far hidden, flavoenzyme-catalyzed chemistries exit.</p

Flavin-Tag:A Facile Method for Site-Specific Labeling of Proteins with a Flavin Fluorophore

Site-specific protein labeling methods are highly valuable tools for research and applications. We present a new protein labeling method that allows covalent attachment of a chromo-and fluorogenic flavin (FMN) to any targeted protein using a short flavinylation peptide-Tag. We show that this peptide can be as short as 7 residues and can be located at the N-Terminus, C-Terminus, or in internal regions of the target protein. Analogous to kinase-catalyzed phosphorylation, the flavin is covalently attached via a stable phosphothreonyl linkage. The site-specific covalent tethering of FMN is accomplished by using a bacterial flavin transferase. The covalent coupling of FMN was shown to work in Escherichia coli and Saccharomyces cerevisiae cells and could be performed in vitro, rendering the "Flavin-Tag"method a powerful tool for the selective decoration of proteins with a biocompatible redox-Active fluorescent chromophore

A Tailor-Made Deazaflavin-Mediated Recycling System for Artificial Nicotinamide Cofactor Biomimetics

[Image: see text] Nicotinamide adenine dinucleotide (NAD) and its 2′-phosphorylated form NADP are crucial cofactors for a large array of biocatalytically important redox enzymes. Their high cost and relatively poor stability, however, make them less attractive electron mediators for industrial processes. Nicotinamide cofactor biomimetics (NCBs) are easily synthesized, are inexpensive, and are also generally more stable than their natural counterparts. A bottleneck for the application of these artificial hydride carriers is the lack of efficient cofactor recycling methods. Therefore, we engineered the thermostable F(420):NADPH oxidoreductase from Thermobifida fusca (Tfu-FNO), by structure-inspired site-directed mutagenesis, to accommodate the unnatural N1 substituents of eight NCBs. The extraordinarily low redox potential of the natural cofactor F(420)H(2) was then exploited to reduce these NCBs. Wild-type enzyme had detectable activity toward all selected NCBs, with K(m) values in the millimolar range and k(cat) values ranging from 0.09 to 1.4 min(–1). Saturation mutagenesis at positions Gly-29 and Pro-89 resulted in mutants with up to 139 times higher catalytic efficiencies. Mutant G29W showed a k(cat) value of 4.2 s(–1) toward 1-benzyl-3-acetylpyridine (BAP(+)), which is similar to the k(cat) value for the natural substrate NADP(+). The best Tfu-FNO variants for a specific NCB were then used for the recycling of catalytic amounts of these nicotinamides in conversion experiments with the thermostable ene-reductase from Thermus scotoductus (TsOYE). We were able to fully convert 10 mM ketoisophorone with BAP(+) within 16 h, using F(420) or its artificial biomimetic FOP (FO-2′-phosphate) as an efficient electron mediator and glucose-6-phosphate as an electron donor. The generated toolbox of thermostable and NCB-dependent Tfu-FNO variants offers powerful cofactor regeneration biocatalysts for the reduction of several artificial nicotinamide biomimetics at both ambient and high temperatures. In fact, to our knowledge, this enzymatic method seems to be the best-performing NCB-recycling system for BNAH and BAPH thus far

Elevated serum level and altered glycosylation of _1-acid glycoprotein in hyperimmunoglobulinemia D and periodic fever syndrome: evidence for persistent inflammation

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Конференции

Background Polypharmacy poses threats to patients’ health. The Systematic Tool to Reduce Inappropriate Prescribing (STRIP) is a drug optimization process for conducting medication reviews in primary care. To effectively and efficiently incorporate this method into daily practice, the STRIP Assistant—a decision support system that aims to assist physicians with the pharmacotherapeutic analysis of patients’ medical records—has been developed. It generates context-specific advice based on clinical guidelines. Objective The aim of this study was to validate the STRIP Assistant’s usability as a tool for physicians to optimize medical records for polypharmacy patients. Methods In an online experiment, 42 physicians were asked to optimize medical records for two comparable polypharmacy patients, one in their usual manner and one using the STRIP Assistant. Changes in effectiveness were measured by comparing respondents’ optimized medicine prescriptions with medication prepared by an expert panel of two geriatrician-pharmacologists. Efficiency was operationalized by recording the time the respondents took to optimize the two cases. User satisfaction was measured with the System Usability Scale (SUS). Independent and paired t tests were used for analysis. Results Medication optimization significantly improved with the STRIP Assistant. Appropriate decisions increased from 58 % without the STRIP Assistant to 76 % with it (p < 0.0001). Inappropriate decisions decreased from 42 % without the STRIP Assistant to 24 % with it (p < 0.0001). Participants spent significantly more time optimizing medication with the STRIP Assistant (24 min) than without it (13 min; p < 0.0001). They assigned it a below-average SUS score of 63.25. Conclusion The STRIP Assistant improves the effectiveness of medication reviews for polypharmacy patients

Photophysics of the electronic states S0 and S1 for the coplanar molecular structures of the α,ω-diphenylpolyenes DPH and DPO

Spectroscopy of the monoclinic and orthorhombic crystalline forms of all-trans-diphenylhexatriene (DPH) and all-trans-diphenyloctatetraene (DPO) show absorption and emission bands that do not generate the widely known Stokes shift of the polyene compounds, discovered by Hausser et al. in 1953 and repeatedly studied over the last 60 years. It can be concluded from our study that the crystallization system, whether in a monoclinic or orthorhombic system, does not significantly influence the photophysics of DPH and DPO in the crystal phas

Serum bile acids associate with liver volume in polycystic liver disease and decrease upon treatment with lanreotide

Background: Polycystic liver disease (PLD) is a common extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD). Bile acids may play a role in PLD pathogenesis. We performed a post-hoc exploratory analysis of bile acids in ADPKD patients, who had participated in a trial on the effect of a somatostatin analogue. Our hypothesis was that serum bile acid levels increase in PLD, and that lanreotide, which reduces liver growth, may also reduce bile acid levels. Furthermore, in PLD, urinary excretion of bile acids might contribute to renal disease. Methods:With liquid chromatography-mass spectrometry, 11 bile acids in serum and 6 in urine were quantified in 105 PLD ADPKD patients and 52 age-, sex-, mutation- and eGFR-matched non-PLD ADPKD patients. Sampling was done at baseline and after 120 weeks of either lanreotide or standard care. Results: Baseline serum levels of taurine- and glycine-conjugated bile acids were higher in patients with larger livers. In PLD patients, multiple bile acids decreased upon treatment with lanreotide but remained stable in untreated subjects. Changes over time did not correlate with changes in liver volume. Urine bile acid levels did not change and did not correlate with renal disease progression. Conclusion: In ADPKD patients with PLD, baseline serum bile acids were associated with liver volume. Lanreotide reduced bile acid levels and has previously been shown to reduce liver volume. However, in this study, the decrease in bile acids was not associated with the change in liver volume.</p

Structure of an Engineered Porcine Phospholipase A2 with Enhanced Activity at 2.1 Å Resolution. Comparison with the Wild-type Porcine and Crotalus atrox Phospholipase A2

The crystal structure of an engineered phospholipase A2 with enhanced activity has been refined to an R-factor of 18.6% at 2.1 Å resolution using a combination of molecular dynamics refinement by the GROMOS package and least-squares refinement by TNT. This mutant phospholipase was obtained previously by deleting residues 62 to 66 in porcine pancreatic phospholipase A2, and changing Asp59 to Ser, Ser60 to Gly and Asn67 to Tyr. The refined structure allowed a detailed comparison with wild-type porcine and Crotalus atrox phospholipase A2. The conformation of the deletion region appears to be intermediate between that in those two enzymes. The residues in the active center are virtually the same. An internal hydrophobic area occupied by Phe63 in the wild-type porcine phospholipase A2 is kept as conserved as possible by local rearrangement of neighboring atoms. In the mutant structure, this hydrophobic pocket is now occupied by the disulfide bond between residues 61 and 91. A detailed description of the second binding site for a calcium ion in this enzyme is given