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Emily P Balskus - One of the best experts on this subject based on the ideXlab platform.
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the l alanosine gene cluster encodes a pathway for diazeniumdiolate biosynthesis
ChemBioChem, 2020Co-Authors: Monica E Mccallum, Christine Zheng, Jennifer X Wang, Emily P BalskusAbstract:N-Nitroso-containing natural products are bioactive metabolites with antibacterial and anticancer properties. In particular, compounds containing the diazeniumdiolate (N-Nitrosohydroxylamine) Group display a wide range of bioactivities ranging from cytotoxicity to metal chelation. Despite the importance of this structural motif, knowledge of its biosynthesis is limited. Herein we describe the discovery of a biosynthetic gene cluster in Streptomyces alanosinicus ATCC 15710 responsible for producing the diazeniumdiolate natural product l-alanosine. Gene disruption and stable isotope feeding experiments identified essential biosynthetic genes and revealed the source of the N-Nitroso Group. Additional biochemical characterization of the biosynthetic enzymes revealed that the non-proteinogenic amino acid l-2,3-diaminopropionic acid (l-Dap) is synthesized and loaded onto a free-standing peptidyl carrier protein (PCP) domain in l-alanosine biosynthesis, which we propose may be a mechanism of handling unstable intermediates generated en route to the diazeniumdiolate. These discoveries will facilitate efforts to determine the biochemistry of diazeniumdiolate formation.
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the l alanosine gene cluster encodes a pathway for diazeniumdiolate biosynthesis
bioRxiv, 2019Co-Authors: Monica E Mccallum, Christine Zheng, Jennifer X Wang, Emily P BalskusAbstract:N-Nitroso-containing natural products are bioactive metabolites with antibacterial and anticancer properties. In particular, compounds containing the diazeniumdiolate (N-Nitrosohydroxylamine) Group display a wide range of bioactivities ranging from cytotoxicity to metal chelation. Despite the importance of this structural motif, knowledge of its biosynthesis is limited. Herein, we describe the discovery of a biosynthetic gene cluster in Streptomyces alanosinicus ATCC 15710 responsible for producing the diazeniumdiolate natural product O_SCPCAPLC_SCPCAP-alanosine. Gene disruption and stable isotope feeding experiments identified essential biosynthetic genes and revealed the nitrogen source of the N-Nitroso Group. Additional biochemical characterization of the biosynthetic enzymes revealed that the non-proteinogenic amino acid O_SCPCAPLC_SCPCAP-2,3-diaminopropionic acid (O_SCPCAPLC_SCPCAP-Dap) is synthesized and loaded onto a peptidyl carrier protein (PCP) domain in O_SCPCAPLC_SCPCAP-alanosine biosynthesis, which we propose may be a mechanism of handling unstable intermediates generated en route to the diazeniumdiolate. This research framework will facilitate efforts to determine the biochemistry of diazeniumdiolate formation.
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an n nitrosating metalloenzyme constructs the pharmacophore of streptozotocin
Nature, 2019Co-Authors: Roman Rohac, A J Mitchell, Amie K Boal, Emily P BalskusAbstract:Small molecules containing the N-Nitroso Group, such as the bacterial natural product streptozotocin, are prominent carcinogens1,2 and important cancer chemotherapeutics3,4. Despite the considerable importance of this functional Group to human health, enzymes dedicated to the assembly of the N-Nitroso unit have not been identified. Here we show that SznF, a metalloenzyme from the biosynthesis of streptozotocin, catalyses an oxidative rearrangement of the guanidine Group of Nω-methyl-L-arginine to generate an N-Nitrosourea product. Structural characterization and mutagenesis of SznF reveal two separate active sites that promote distinct steps in this transformation using different iron-containing metallocofactors. This biosynthetic reaction, which has little precedent in enzymology or organic synthesis, expands the catalytic capabilities of non-haem-iron-dependent enzymes to include N-N bond formation. We find that biosynthetic gene clusters that encode SznF homologues are widely distributed among bacteria-including environmental organisms, plant symbionts and human pathogens-which suggests an unexpectedly diverse and uncharacterized microbial reservoir of bioactive N-Nitroso metabolites.
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an n nitrosating metalloenzyme constructs the pharmacophore of streptozotocin
Nature, 2019Co-Authors: Tai L Ng, Roman Rohac, A J Mitchell, Amie K Boal, Emily P BalskusAbstract:Small molecules containing the N-Nitroso Group, such as the bacterial natural product streptozotocin, are prominent carcinogens1,2 and important cancer chemotherapeutics3,4. Despite the considerable importance of this functional Group to human health, enzymes dedicated to the assembly of the N-Nitroso unit have not been identified. Here we show that SznF, a metalloenzyme from the biosynthesis of streptozotocin, catalyses an oxidative rearrangement of the guanidine Group of Nω-methyl-l-arginine to generate an N-Nitrosourea product. Structural characterization and mutagenesis of SznF reveal two separate active sites that promote distinct steps in this transformation using different iron-containing metallocofactors. This biosynthetic reaction, which has little precedent in enzymology or organic synthesis, expands the catalytic capabilities of non-haem-iron-dependent enzymes to include N–N bond formation. We find that biosynthetic gene clusters that encode SznF homologues are widely distributed among bacteria—including environmental organisms, plant symbionts and human pathogens—which suggests an unexpectedly diverse and uncharacterized microbial reservoir of bioactive N-Nitroso metabolites. The metalloenzyme SznF catalyses the formation of an N–N bond in the biosynthesis of streptozotocin, providing insights into the enzymatic assembly of an N-Nitroso Group.
Lara Ribeiro - One of the best experts on this subject based on the ideXlab platform.
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Nitroso Group transfer in s Nitrosocysteine evidence of a new decomposition pathway for Nitrosothiols
Journal of Organic Chemistry, 2005Co-Authors: Claudia Guadalupe Adam, Luis Garciario, J R Leis, Lara RibeiroAbstract:The rate of S-Nitrosocysteine decomposition in a pH range between 0.7 < pH < 13 exhibits first- and second-order dependence on total cysteine concentration. The second-order term is only observed for pH values between 6.9 < pH < 12. Both first- and second-order terms show a complex dependence on the acidity of the medium. They increase with increasing pH, reaching a maximum value around pH = 8 and then decrease with further increase in pH. An analysis of the reaction products reveals the absence of nitrite ion and ammonia. No evidence of catalysis by copper ions is observed. These results suggest the existence of a new decomposition pathway for S-Nitrosocysteine, which proceeds via an intramolecular Nitroso Group transfer producing a primary N-nitrosamine that decomposes rapidly to give the corresponding diazonium salt. The Nitroso Group transfer reaction occurs intermolecularly for the decomposition pathway exhibiting a quadratic dependence on cysteine concentration. Both Nitroso Group transfer pathways ...
Jin Zhu - One of the best experts on this subject based on the ideXlab platform.
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c h activation based traceless synthesis via electrophilic removal of a directing Group rhodium iii catalyzed entry into indoles from n Nitroso and α diazo β keto compounds
Organic Letters, 2016Co-Authors: Jie Wang, Mingyang Wang, Kehao Chen, Shanke Zha, Chao Song, Jin ZhuAbstract:A distinct C–H activation-based traceless synthetic protocol via electrophilic removal of a directing Group is reported, complementing the currently exclusively used nucleophilic strategy. Rh(III)-catalyzed, N-Nitroso-directed C–H activation allows the development of a traceless, atom- and step-economic, cascade approach for the synthesis of indole skeletons, starting from readily available N-Nitroso and α-diazo-β-keto compounds. Importantly, the cyclization/denitrosation reaction represents a hitherto unobserved reactivity pattern for the N-Nitroso Group.
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C–H Activation-Based Traceless Synthesis via Electrophilic Removal of a Directing Group. Rhodium(III)-Catalyzed Entry into Indoles from N‑Nitroso and α‑Diazo-β-keto Compounds
2016Co-Authors: Jie Wang, Mingyang Wang, Kehao Chen, Shanke Zha, Chao Song, Jin ZhuAbstract:A distinct C–H activation-based traceless synthetic protocol via electrophilic removal of a directing Group is reported, complementing the currently exclusively used nucleophilic strategy. Rh(III)-catalyzed, N-Nitroso-directed C–H activation allows the development of a traceless, atom- and step-economic, cascade approach for the synthesis of indole skeletons, starting from readily available N-Nitroso and α-diazo-β-keto compounds. Importantly, the cyclization/denitrosation reaction represents a hitherto unobserved reactivity pattern for the N-Nitroso Group
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rhodium iii catalyzed indole synthesis using n n bond as an internal oxidant
Journal of the American Chemical Society, 2013Co-Authors: Baoqing Liu, Chao Song, Chao Sun, Shuguang Zhou, Jin ZhuAbstract:We report herein a Rh(III)-catalyzed cyclization of N-Nitrosoanilines with alkynes for streamlined synthesis of indoles. The synthetic protocol features a distinct internal oxidant, N–N bond, as a reactive handle for catalyst turnover, as well as a hitherto tantalizingly elusive intermolecular redox-neutral manifold, predicated upon C–H activation, for the formation of a five-membered azaheterocycle. The compatibility of seemingly dichotomous acidic and basic conditions ensures reaction versatility for multifarious synthetic contexts. The tolerance of an array of auxiliary functional Groups potentially permits predefined, programmable substitution patterns to be incorporated into the indole scaffold. Comprehensive mechanistic studies, under acidic condition, support [RhCp*]2+ as generally the catalyst resting state (switchable to [RhCp*(OOCtBu)]+ under certain circumstance) and C–H activation as the turnover-limiting step. Given the variety of covalent linkages available for the Nitroso Group, this labile...
Lawrence K Silbart - One of the best experts on this subject based on the ideXlab platform.
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cloning and characterization of a hybridoma secreting a 4 methylnitrosamino 1 3 pyridyl 1 butanone nnk specific monoclonal antibody and recombinant f ab
Toxins, 2013Co-Authors: Heather Wanczyk, Tolga Barker, Debra Rood, Daniel I Zapata, Amy R Howell, Stewart K Richardson, John W Zinckgraf, Gregory Marusov, Michael A Lynes, Lawrence K SilbartAbstract:Smokeless tobacco products have been associated with increased risks of oro-pharyngeal cancers, due in part to the presence of tobacco-specific nitrosamines (TSNAs) such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). These potent carcinogens are formed during tobacco curing and as a result of direct nitrosation reactions that occur in the oral cavity. In the current work we describe the isolation and characterization of a hybridoma secreting a high-affinity, NNK-specific monoclonal antibody. A structurally-related benzoyl derivative was synthesized to facilitate coupling to NNK-carrier proteins, which were characterized for the presence of the N-Nitroso Group using the Griess reaction, and used to immunize BALB/c mice. Splenocytes from mice bearing NNK-specific antibodies were used to create hybridomas. Out of four, one was selected for subcloning and characterization. Approximately 99% of the monoclonal antibodies from this clone were competitively displaced from plate-bound NNKB conjugates in the presence of free NNK. The affinity of the monoclonal antibody to the NNKB conjugates was Kd = 2.93 nM as determined by surface plasmon resonance. Free nicotine was a poor competitor for the NNKB binding site. The heavy and light chain antibody F(ab) fragments were cloned, sequenced and inserted in tandem into an expression vector, with an FMDV Furin 2A cleavage site between them. Expression in HEK 293 cells revealed a functional F(ab) with similar binding features to that of the parent hybridoma. This study lays the groundwork for synthesizing transgenic tobacco that expresses carcinogen-sequestration properties, thereby rendering it less harmful to consumers.
Zbigniew Wrobel - One of the best experts on this subject based on the ideXlab platform.
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reactivity and substituent effects in the cyclization of n aryl 2 Nitrosoanilines to phenazines
Tetrahedron, 2017Co-Authors: Zbigniew Wrobel, Karolina Plichta, Andrzej KwastAbstract:Reactivity of variously substituted N-aryl-2-Nitrosoanilines in the reaction of cyclization leading to phenazine derivatives, carried out in the presence of N,O-bis(trimethylsilyl)acetamide (BSA), was estimated on the base of the observed reaction times. A strong opposite effect of substituents located at position para to the Nitroso Group and those located para to the amino Group in the side ring was observed. Mechanistic explanation, based on the electronic properties of the substituents and their mesomeric effects, was presented. The usefulness of the obtained data for the designed syntheses of phenazines was exposed.
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a short preparation of pyrroloquinoxalinones via a cascade reaction of n aryl 5 alkylamino 2 Nitrosoanilines with methyl 2 cyanoalkanoates unexpected direction of nucleophilic substitution of hydrogen
ChemInform, 2013Co-Authors: Magdalena Krolikiewicz, Piotr Cmoch, Zbigniew WrobelAbstract:The bisheteroannulation to produce the title compounds (III) involves condensation of a cyanoester anion with the Nitroso Group of substrates (I), unusual nucleophilic substitution of hydrogen with a second anion, and double intramolecular acylation.
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A Short Preparation of Pyrroloquinoxalinones via a Cascade Reaction of N-Aryl-5-alkylamino-2-Nitrosoanilines with Methyl 2-Cyanoalkanoates: Unexpected Direction of Nucleophilic Substitution of Hydrogen
Synlett, 2013Co-Authors: Magdalena Krolikiewicz, Piotr Cmoch, Zbigniew WrobelAbstract:N -Aryl-2-Nitrosoanilines possessing 5-alkylamino Groups undergo a bisheteroannulation reaction with anions of 2-cyanoalkanecarboxylates resulting in pyrroloquinoxalinone derivatives. The cascade reaction involves condensation of the cyanoester anions with the Nitroso Group, unusual nucleophilic substitution of hydrogen in the Nitrosoaniline-derived intermediate with the second carbanion molecule, and double intramolecular acylation of the amino functions.
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regioselective aromatic nucleophilic substitution in n aryl 2 Nitrosoanilines with oxygen and nitrogen nucleophiles
Synthesis, 2012Co-Authors: Zbigniew Wrobel, Karolina Stachowska, Andrzej KwastAbstract:Aromatic nucleophilic substitution of halogens in N-aryl-2-Nitrosoanilines with ammonia, alkylamines and alkoxide ions proceeds efficiently and highly regioselectively in the position para to the Nitroso Group. When two halogen atoms ortho and para are present, the latter is substituted exclusively. Oxidative substitution of hydrogen at the unsubstituted ortho position of the Nitrosoaniline ring does not compete with substitution of para halogen atoms. The reaction allows the synthesis of N-aryl-2-Nitrosoanilines which cannot be obtained according to known methods.
