On the structure of intermediate adducts arising from dithionite reduction of pyridinium salts: a novel class of derivatives of the parent sulfinic acid

Carelli, Vincenzo; Liberatore, Felice; Scipione, Luigi; Musio, Roberta; Sciacovelli, O.

doi:10.1016/s0040-4039(99)02251-0

Cited by 21 publications

(13 citation statements)

References 27 publications

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“…This reaction resembles the reduction of the pyridinium salts by dithionite in the coenzyme NAD + (55–57). To test this hypothesis, we incubated the TpTSO 2 − with the enzyme in a pH 7.0 buffer for 1 hr.…”

Section: Resultsmentioning

confidence: 87%

“…No TpT was found as analyzed by HPLC. Moreover, we repeated the experiments in the pH 7.0 and 9.0 Tris buffer in the presence or absence of UV light respectively, as the neutral or mildly basic condition is suggested to favor the SO 2 elimination (55–57). Analysis of the reaction products revealed that TpTSO 2 − is stable under these conditions and no TpT was observed either.…”

Section: Resultsmentioning

confidence: 99%

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Mechanistic Studies of the Spore Photoproduct Lyase via a Single Cysteine Mutation

et al. 2012

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5-thyminyl-5,6-dihydrothymine (also called spore photoproduct or SP) is the exclusive DNA photo-damage product in bacterial endospores. It is repaired by a radical SAM (S-adenosylmethionine) enzyme, the spore photoproduct lyase (SPL), at the bacterial early germination phase. Our previous studies proved that SPL utilizes the 5′-dA• generated by SAM cleavage reaction to abstract the H6proR atom to initiate the SP repair process. The resulting thymine allylic radical was suggested to take an H atom from an unknown protein source, most likely the cysteine 141. Here we show that C141 can be readily alkylated in the native SPL by iodoacetamide treatment, suggesting that it is accessible to the TpT radical. SP repair by the SPL C141A mutant yields TpTSO2− and TpT simultaneously from the very beginning of the reaction; no lag phase is observed for the TpTSO2− formation. Should any other protein residue serve as the H donor, its presence would result in TpT as the major product at least for the first enzyme turnover. These observations provide strong evidence to support C141 as the direct H atom donor. Moreover, due to the lack of this intrinsic H donor, the C141A mutant produces TpT via an unprecedented thymine cation radical reduction (proton coupled electron transfer) process, contrasting to the H atom transfer mechanism in the WT SPL reaction. The C141A mutant repairs SP at a rate which is ~3-fold slower than the WT enzyme. Formation of TpTSO2− and TpT exhibit a Vmax deuterium kinetic isotope effect (KIE) of 1.7 ± 0.2 respectively, which is smaller than the DVmax KIE of 2.8 ± 0.3 determined in the WT SPL reaction. These findings suggest that removing the intrinsic H atom donor disturbs the rate-limiting process in the enzyme catalysis. As expected, the pre-reduced C141A mutant only supports ~ 0.4 turnover, which is in sharp contrast to the > 5 turnovers exhibited by the WT SPL reaction, suggesting that the enzyme catalytic cycle (SAM regeneration) is disrupted by this single mutation.

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Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Mechanistic Studies of the Spore Photoproduct Lyase via a Single Cysteine Mutation

et al. 2012

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“…It is well known that dithionite reduction appears to be applicable to all pyridinium salts bearing electron‐withdrawing substituents in the 3‐ or 3,5‐positions, affording exclusively the corresponding 1,4‐dihydropyridines, as final products. In the course of the reduction, formed intermediate adducts have been identified as sulfinate S ‐anions . Furthermore, these adducts are stable in strong alkaline solutions, whereas at low alkaline pH values, these were protonated to sulfinate, which promptly decomposed into 1,4‐dihydropyridines following SO 2 elimination .…”

Section: Resultsmentioning

confidence: 99%

Efficient Synthesis of 3,5‐Dicarbamoyl‐1,4‐dihydropyridines from Pyridinium Salts: Key Molecules in Understanding NAD(P)⁺/NAD(P)H Pathways

Mellini

Vita

Rienzo

et al. 2014

Journal of Heterocyclic Chem

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3,5-Dicarbamoyl-1,4-dihydropyridines were prepared in high yields using a green protocol by reduction\ud of the corresponding pyridinium salts in aqueous buffered sodium dithionite solutions. The pH value is a\ud fundamental parameter for the reduction step and depends on the nature of substituent groups at positions\ud 1, 3, and 5 of the pyridinium salts. These 3,5-dicarbamoyl dihydropyridines show a lower tendency towards\ud oxidation and a higher stability than N-benzyl-3-carbamoyl-1,4-dihydropyridine at low pH value

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“…Then the nicotinoyl residue was converted to trigonellyl (T + ) using MeI. After the well-established reduction using Na 2 S 2 O 4 [ 18 ] the BTCDSs were obtained. This reduction was conveniently monitored by UV spectroscopy (Lambda 11 UV/Vis Perkin Elmer spectrometer; Perkin Elmer Anal.…”

Section: Synthesismentioning

confidence: 99%

The Utility of Oligopeptidase in Brain-Targeting Delivery of an Enkephalin Analogue by Prodrug Design

Prókai-Tátrai¹,

Kim²,

Prókai³

2008

Open Med Chem J

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In a brain-targeting prodrug approach for a metabolically stable enkephalin analogue DADLE, specific enzymes are utilized for in vivo prodrug activation. Prolyl oligopeptidase (POP) may be especially useful in this regard. In vitro metabolic stability of the putative metabolites of prodrugs having various “spacers” has shown that POP provides significantly faster release of DADLE from conjugates having dipeptidyl spacer (specifically Xaa-Pro or Xaa-Ala) than alternative peptidases utilized when single amino acids are used as spacers. In vitro half-lives measured in rat brain homogenate showed excellent correlation with CNS-mediated analgesia using the tail-flick model in rats providing, thus, an in vivo substantiation of the prodrug approach relying on POP as the peptidase to release DADLE.

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On the structure of intermediate adducts arising from dithionite reduction of pyridinium salts: a novel class of derivatives of the parent sulfinic acid

Cited by 21 publications

References 27 publications

Mechanistic Studies of the Spore Photoproduct Lyase via a Single Cysteine Mutation

Mechanistic Studies of the Spore Photoproduct Lyase via a Single Cysteine Mutation

Efficient Synthesis of 3,5‐Dicarbamoyl‐1,4‐dihydropyridines from Pyridinium Salts: Key Molecules in Understanding NAD(P)⁺/NAD(P)H Pathways

The Utility of Oligopeptidase in Brain-Targeting Delivery of an Enkephalin Analogue by Prodrug Design

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On the structure of intermediate adducts arising from dithionite reduction of pyridinium salts: a novel class of derivatives of the parent sulfinic acid

Cited by 21 publications

References 27 publications

Mechanistic Studies of the Spore Photoproduct Lyase via a Single Cysteine Mutation

Mechanistic Studies of the Spore Photoproduct Lyase via a Single Cysteine Mutation

Efficient Synthesis of 3,5‐Dicarbamoyl‐1,4‐dihydropyridines from Pyridinium Salts: Key Molecules in Understanding NAD(P)+/NAD(P)H Pathways

The Utility of Oligopeptidase in Brain-Targeting Delivery of an Enkephalin Analogue by Prodrug Design

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Efficient Synthesis of 3,5‐Dicarbamoyl‐1,4‐dihydropyridines from Pyridinium Salts: Key Molecules in Understanding NAD(P)⁺/NAD(P)H Pathways