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Publications - Bioorganic Chemistry

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Publications

El Amerany, F.; Meddich, A.; Wahbi, S.; Porzel, A.; Taourirte, M.; Rhazi, M.; Hause, B. Foliar Application of Chitosan Increases Tomato Growth and Influences Mycorrhization and Expression of Endochitinase-Encoding Genes Int J Mol Sci 21, 535, (2020) DOI: 10.3390/ijms21020535

Nowadays, applying bio-organic fertilizer (e.g., chitosan, Ch) or integrating beneficial microorganisms (e.g., arbuscular mycorrhizal fungi, AMF) are among the successful strategies to promote plant growth. Here, the effect of two application modes of Ch (foliar spray or root treatment) and Ch-derived nanoparticles (NPs) on tomato plants colonized with the AMF Rhizophagus irregularis were analyzed, thereby focusing on plant biomass, flowering and mycorrhization. An increase of shoot biomass and flower number was observed in arbuscular mycorrhizal (AM) plants sprayed with Ch. The interaction with AMF, however, was reduced as shown by decreased mycorrhization rates and AM-specific gene expression. To get insights into Ch effect on mycorrhization, levels of sugars, jasmonates, abscisic acid, and the expression of two chitinase-encoding genes were determined in mycorrhizal roots. Ch had no effect on sugar and phytohormone levels, but the reduced mycorrhization was correlated with down- and upregulated expression of Chi3 and Chi9, respectively. In contrast, application of NPs to leaves and Ch applied to the soil did not show any effect, neither on mycorrhization rate nor on growth of mycorrhizal plants. Concluding, Ch application to leaves enhanced plant growth and flowering and reduced interaction with AMF, whereas root treatment did not affect these parameters.
Publications

Leonova, T.; Popova, V.; Tsarev, A.; Henning, C.; Antonova, K.; Rogovskaya, N.; Vikhnina, M.; Baldensperger, T.; Soboleva, A.; Dinastia, E.; Dorn, M.; Shiroglasova, O.; Grishina, T.; Balcke, G. U.; Ihling, C.; Smolikova, G.; Medvedev, S.; Zhukov, V. A.; Babakov, V.; Tikhonovich, I. A.; Glomb, M. A.; Bilova, T.; Frolov, A. Does Protein Glycation Impact on the Drought-Related Changes in Metabolism and Nutritional Properties of Mature Pea (Pisum sativum L.) Seeds? Int J Mol Sci 21, 567, (2020) DOI: 10.3390/ijms21020567

Protein glycation is usually referred to as an array of non-enzymatic post-translational modifications formed by reducing sugars and carbonyl products of their degradation. The resulting advanced glycation end products (AGEs) represent a heterogeneous group of covalent adducts, known for their pro-inflammatory effects in mammals, and impacting on pathogenesis of metabolic diseases and ageing. In plants, AGEs are the markers of tissue ageing and response to environmental stressors, the most prominent of which is drought. Although water deficit enhances protein glycation in leaves, its effect on seed glycation profiles is still unknown. Moreover, the effect of drought on biological activities of seed protein in mammalian systems is still unstudied with respect to glycation. Therefore, here we address the effects of a short-term drought on the patterns of seed protein-bound AGEs and accompanying alterations in pro-inflammatory properties of seed protein in the context of seed metabolome dynamics. A short-term drought, simulated as polyethylene glycol-induced osmotic stress and applied at the stage of seed filling, resulted in the dramatic suppression of primary seed metabolism, although the secondary metabolome was minimally affected. This was accompanied with significant suppression of NF-kB activation in human SH-SY5Y neuroblastoma cells after a treatment with protein hydrolyzates, isolated from the mature seeds of drought-treated plants. This effect could not be attributed to formation of known AGEs. Most likely, the prospective anti-inflammatory effect of short-term drought is related to antioxidant effect of unknown secondary metabolite protein adducts, or down-regulation of unknown plant-specific AGEs due to suppression of energy metabolism during seed filling.
Publications

Böhme, B.; Moritz, B.; Wendler, J.; Hertel, T. C.; Ihling, C.; Brandt, W.; Pietzsch, M. Enzymatic activity and thermoresistance of improved microbial transglutaminase variants Amino Acids 52, 313-326, (2020) DOI: 10.1007/s00726-019-02764-9

Microbial transglutaminase (MTG, EC 2.3.2.13) of Streptomyces mobaraensis is widely used in industry for its ability to synthesize isopeptide bonds between the proteinogenic side chains of glutamine and lysine. The activated wild-type enzyme irreversibly denatures at 60 °C with a pseudo-first-order kinetics and a half-life time (t1/2) of 2 min. To increase the thermoresistance of MTG for higher temperature applications, we generated 31 variants based on previous results obtained by random mutagenesis, DNA shuffling and saturation mutagenesis. The best variant TG16 with a specific combination of five of seven substitutions (S2P, S23Y, S24 N, H289Y, K294L) shows a 19-fold increased half-life at 60 °C (t1/2 = 38 min). As measured by differential scanning fluorimetry, the transition point of thermal unfolding was increased by 7.9 °C. Also for the thermoresistant variants, it was shown that inactivation process follows a pseudo-first-order reaction which is accompanied by irreversible aggregation and intramolecular self-crosslinking of the enzyme. Although the mutations are mostly located on the surface of the enzyme, kinetic constants determined with the standard substrate CBZ-Gln-Gly-OH revealed a decrease in KM from 8.6 mM (± 0.1) to 3.5 mM (± 0.1) for the recombinant wild-type MTG and TG16, respectively. The improved performance of TG16 at higher temperatures is exemplary demonstrated with the crosslinking of the substrate protein β-casein at 60 °C. Using molecular dynamics simulations, it was shown that the increased thermoresistance is caused by a higher backbone rigidity as well as increased hydrophobic interactions and newly formed hydrogen bridges.
Publications

Guerra, T.; Schilling, S.; Hake, K.; Gorzolka, K.; Sylvester, F.-P.; Conrads, B.; Westermann, B.; Romeis, T. Calcium‐dependent protein kinase 5 links calcium‐signaling with N‐Hydroxy‐L‐pipecolic acid‐ and SARD1‐dependent immune memory in systemic acquired resistance New Phytol 225, 310-325, (2020) DOI: 10.1111/nph.16147

Systemic acquired resistance (SAR) prepares infected plants for faster and stronger defense activation upon subsequent attacks. SAR requires an information relay from primary infection to distal tissue and the initiation and maintenance of a self‐maintaining phytohormone salicylic acid (SA)‐defense loop.In spatial and temporal resolution, we show that calcium‐dependent protein kinase CPK5 contributes to immunity and SAR. In local basal resistance, CPK5 functions upstream of SA synthesis, perception, and signaling. In systemic tissue, CPK5 signaling leads to accumulation of SAR‐inducing metabolite N‐hydroxy‐L‐pipecolic acid (NHP) and SAR marker genes, including Systemic Acquired Resistance Deficient 1 (SARD1)Plants of increased CPK5, but not CPK6, signaling display an ‘enhanced SAR’ phenotype towards a secondary bacterial infection. In the sard1‐1 background, CPK5‐mediated basal resistance is still mounted, but NHP concentration is reduced and enhanced SAR is lost.The biochemical analysis estimated CPK5 half maximal kinase activity for calcium, K50 [Ca2+], to be c. 100 nM, close to the cytoplasmic resting level. This low threshold uniquely qualifies CPK5 to decode subtle changes in calcium, a prerequisite to signal relay and onset and maintenance of priming at later time points in distal tissue. Our data explain why CPK5 functions as a hub in basal and systemic plant immunity.
Publications

Laub, A.; Sendatzki, A.-K.; Palfner, G.; Wessjohann, L. A.; Schmidt, J.; Arnold, N. HPTLC-DESI-HRMS-Based Profiling of Anthraquinones in Complex Mixtures—A Proof-of-Concept Study Using Crude Extracts of Chilean Mushrooms Foods 9, 156, (2020) DOI: 10.3390/foods9020156

High-performance thin-layer chromatography (HPTLC) coupled with negative ion desorption electrospray ionization high-resolution mass spectrometry (DESI-HRMS) was used for the analysis of anthraquinones in complex crude extracts of Chilean dermocyboid Cortinarii. For this proof-of-concept study, the known anthraquinones emodin, physcion, endocrocin, dermolutein, hypericin, and skyrin were identified by their elemental composition. HRMS also allowed the differentiation of the investigated anthraquinones from accompanying compounds with the same nominal mass in the crude extracts. An investigation of the characteristic fragmentation pattern of skyrin in comparison with a reference compound showed, exemplarily, the feasibility of the method for the determination of these coloring, bioactive and chemotaxonomically important marker compounds. Accordingly, we demonstrate that the coupling of HPTLC with DESI-HRMS represents an advanced and efficient technique for the detection of anthraquinones in complex matrices. This analytical approach may be applied in the field of anthraquinone-containing food and plants such as Rheum spp. (rhubarb), Aloe spp., Morinda spp., Cassia spp. and others. Furthermore, the described method can be suitable for the analysis of anthraquinone-based colorants and dyes, which are used in the food, cosmetic, and pharmaceutical industry.
Publications

Farag, M. A.; Abdelwareth, A.; Sallam, I. E.; el Shorbagi, M.; Jehmlich, N.; Fritz-Wallace, K.; Serena Schäpe, S.; Rolle-Kampczyk, U.; Ehrlich, A.; Wessjohann, L. A.; von Bergen, M. Metabolomics reveals impact of seven functional foods on metabolic pathways in a gut microbiota model J Adv Res 23, 47-59, (2020) DOI: 10.1016/j.jare.2020.01.001

Functional food defined as dietary supplements that in addition to their nutritional values, can beneficially modulate body functions becomes more and more popular but the reaction of the intestinal microbiota to it is largely unknown. In order to analyse the impact of functional food on the microbiota itself it is necessary to focus on the physiology of the microbiota, which can be assessed in a whole by untargeted metabolomics. Obtaining a detailed description of the gut microbiota reaction to food ingredients can be a key to understand how these organisms regulate and bioprocess many of these food components. Extracts prepared from seven chief functional foods, namely green tea, black tea, Opuntia ficus-indica (prickly pear, cactus pear), black coffee, green coffee, pomegranate, and sumac were administered to a gut consortium culture encompassing 8 microbes which are resembling, to a large extent, the metabolic activities found in the human gut. Samples were harvested at 0.5 and 24 h post addition of functional food extract and from blank culture in parallel and analysed for its metabolites composition using gas chromatography coupled to mass spectrometry detection (GC-MS). A total of 131 metabolites were identified belonging to organic acids, alcohols, amino acids, fatty acids, inorganic compounds, nitrogenous compounds, nucleic acids, phenolics, steroids and sugars, with amino acids as the most abundant class in cultures. Considering the complexity of such datasets, multivariate data analyses were employed to classify samples and investigate how functional foods influence gut microbiota metabolisms. Results from this study provided a first insights regarding how functional foods alter gut metabolism through either induction or inhibition of certain metabolic pathways, i.e. GABA production in the presence of higher acidity induced by functional food metabolites such as polyphenols. Likewise, functional food metabolites i.e., purine alkaloids acted themselves as direct substrate in microbiota metabolism.
Publications

Abbas, G.; Haq, Q. M. I.; Hamaed, A.; Al-Sibani, M.; Hussain, H. Glucagon and Glucagon-like Peptide-1 Receptors: Promising Therapeutic Targets for an Effective Management of Diabetes Mellitus Curr Pharm Des 26, 501-508, (2020) DOI: 10.2174/1381612826666200131143231

G-protein-coupled receptors (GPCRs) are membrane-bound proteins which are responsible for the detection of extracellular stimuli and the origination of intracellular responses. Both glucagon and glucagon-like peptide-1 (GLP-1) receptors belong to G protein-coupled receptor (GPCR) superfamily. Along with insulin, glucagon and GLP-1 are critical hormones for maintaining normal serum glucose within human body. Glucagon generally plays its role in the liver through cyclic adenosine monophosphate (cAMP), where it compensates the action of insulin. GLP-1 is secreted by the L-cells of the small intestine to stimulate insulin secretion and inhibit glucagon action. Despite the extensive research efforts and the multiple approaches adopted, the glycemic control in the case of type-2 diabetes mellitus remains a major challenge. Therefore, a deep understanding of the structure-function relationship of these receptors will have great implications on future therapies in order to maintain a normal glucose level for an extended period of time. The antagonists of glucagon receptor that can effectively block the hepatic glucose production, as a result of glucagon action, are highly desirable for the tuning of the hyperglycemic state in type 2 diabetes mellitus. In the same manner, GLP-1R agonists act as important treatment modalities thanks to their multiple anti-diabetic actions to attain normal glucose level. In this review article, the structural diversity of glucagon and GLP-1 receptors along with their signaling pathways, site-directed mutations and significance in drug discovery against type-2 diabetes will be illustrated. Moreover, the promising non-peptide antagonists of glucagon receptor and agonists of GLP-1 receptor, for the management of diabetes will be presented with elaboration on the structure-activity relationship (SAR).
Publications

Vasco, A. V.; Brode, M.; Méndez, Y.; Valdés, O.; Rivera, D. G.; Wessjohann, L. A. Synthesis of Lactam-Bridged and Lipidated Cyclo-Peptides as Promising Anti-Phytopathogenic Agents Molecules 25, 811, (2020) DOI: 10.3390/molecules25040811

Antimicrobial resistance to conventional antibiotics and the limited alternatives to combat plant-threatening pathogens are worldwide problems. Antibiotic lipopeptides exert remarkable membrane activity, which usually is not prone to fast resistance formation, and often show organism-type selectivity. Additional modes of action commonly complement the bioactivity profiles of such compounds. The present work describes a multicomponent-based methodology for the synthesis of cyclic polycationic lipopeptides with stabilized helical structures. The protocol comprises an on solid support Ugi-4-component macrocyclization in the presence of a lipidic isocyanide. Circular dichroism was employed to study the influence of both macrocyclization and lipidation on the amphiphilic helical structure in water and micellar media. First bioactivity studies against model phytopathogens demonstrated a positive effect of the lipidation on the antimicrobial activity.
Publications

Ricardo, M. G.; Moya, C. G.; Pérez, C. S.; Porzel, A.; Wessjohann, L. A.; Rivera, D. G. Improved Stability and Tunable Functionalization of Parallel β-Sheets via Multicomponent N-Alkylation of the Turn Moiety Angew Chem Int Ed 59, 259-263, (2020) DOI: 10.1002/anie.201912095

In contrast to the myriad of methods available to produce α‐helices and antiparallel β‐sheets in synthetic peptides, just a few are known for the construction of stable, non‐cyclic parallel β‐sheets. Herein, we report an efficient on‐resin approach for the assembly of parallel β‐sheet peptides in which the N‐alkylated turn moiety enhances the stability and gives access to a variety of functionalizations without modifying the parallel strands. The key synthetic step of this strategy is the multicomponent construction of an N‐alkylated turn using the Ugi reaction on varied isocyano‐resins. This four‐component process assembles the orthogonally protected turn fragment and incorporates handles serving for labeling/conjugation purposes or for reducing peptide aggregation. NMR and circular dichroism analyses confirm the better‐structured and more stable parallel β‐sheets in the N‐alkylated peptides compared to the non‐functionalized variants.
Publications

Ricardo, M. G.; Moya, C. G.; Pérez, C. S.; Porzel, A.; Wessjohann, L. A.; Rivera, D. G. Improved Stability and Tunable Functionalization of Parallel β‐Sheets via Multicomponent N‐Alkylation of the Turn Moiety Angew Chem 132, 265-269, (2020) DOI: 10.1002/ange.201912095

In contrast to the myriad of methods available to produce α‐helices and antiparallel β‐sheets in synthetic peptides, just a few are known for the construction of stable, non‐cyclic parallel β‐sheets. Herein, we report an efficient on‐resin approach for the assembly of parallel β‐sheet peptides in which the N‐alkylated turn moiety enhances the stability and gives access to a variety of functionalizations without modifying the parallel strands. The key synthetic step of this strategy is the multicomponent construction of an N‐alkylated turn using the Ugi reaction on varied isocyano‐resins. This four‐component process assembles the orthogonally protected turn fragment and incorporates handles serving for labeling/conjugation purposes or for reducing peptide aggregation. NMR and circular dichroism analyses confirm the better‐structured and more stable parallel β‐sheets in the N‐alkylated peptides compared to the non‐functionalized variants.
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