Oxidation of organic divalent sulfur by iodine. II. Equilibrating thiol-iodine-disulfide-hydrogen iodide system in acetic acid and evidence for sulfenyl iodide intermediates

Danehy, James P.; Doherty, Brendan T.; Egan, Catherine P.

doi:10.1021/jo00816a030

Cited by 37 publications

(25 citation statements)

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“…With these mutant proteins, intramolecular disulfide-bond formation cannot proceed, and reaction with iodide led presumably to the formation a Cys-158 thiol-iodine adduct (Danehy et al, 1971). That such a modification may be responsible for the inhibited activity of the Ph-CCR1-Cys150 mutants is consistent with the known susceptibility of CCR to inhibition by thiolmodifying agents (Goffner et al, 1998;Sonawane et al, 2013).…”

Section: Inferences On Hydroxycinnamoyl-coa Binding and Catalytic Mecmentioning

confidence: 62%

Structural Studies of Cinnamoyl-CoA Reductase and Cinnamyl-Alcohol Dehydrogenase, Key Enzymes of Monolignol Biosynthesis

et al. 2014

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The enzymes cinnamoyl-CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) catalyze the two key reduction reactions in the conversion of cinnamic acid derivatives into monolignol building blocks for lignin polymers in plant cell walls. Here, we describe detailed functional and structural analyses of CCRs from Medicago truncatula and Petunia hybrida and of an atypical CAD (CAD2) from M. truncatula. These enzymes are closely related members of the short-chain dehydrogenase/ reductase (SDR) superfamily. Our structural studies support a reaction mechanism involving a canonical SDR catalytic triad in both CCR and CAD2 and an important role for an auxiliary cysteine unique to CCR. Site-directed mutants of CAD2 (Phe226Ala and Tyr136Phe) that enlarge the phenolic binding site result in a 4-to 10-fold increase in activity with sinapaldehyde, which in comparison to the smaller coumaraldehyde and coniferaldehyde substrates is disfavored by wild-type CAD2. This finding demonstrates the potential exploitation of rationally engineered forms of CCR and CAD2 for the targeted modification of monolignol composition in transgenic plants. Thermal denaturation measurements and structural comparisons of various liganded and unliganded forms of CCR and CAD2 highlight substantial conformational flexibility of these SDR enzymes, which plays an important role in the establishment of catalytically productive complexes of the enzymes with their NADPH and phenolic substrates.

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Section: Inferences On Hydroxycinnamoyl-coa Binding and Catalytic Mecmentioning

confidence: 62%

Structural Studies of Cinnamoyl-CoA Reductase and Cinnamyl-Alcohol Dehydrogenase, Key Enzymes of Monolignol Biosynthesis

et al. 2014

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“…The synthesis of cyclic cystine peptides is exemplified by the protected somatostatin 17 (Scheme 7). As previously in the segment 9 of calcitonin (s. Scheme 6), one cysteine residue in the precursor 16 was protected by a trityl (position 14) and the second by an acetamidomethyl group (position 3). Cyclization of 16 was carried out in methanoVDMF 9 : l at a peptide concentration of l O P 3~ with a 12-fold molar excess of iodine.…”

mentioning

confidence: 81%

“…Charge separation leads to the iodosulfonium ion ii [ 131 which is cleaved to the sulfenyl iodide iii and the trityl carbenium ion. Sulfenyl iodides are assumed to be intermediates in the iodine oxidation of thiols to disulfides [14]. The subsequent formation of the disulfide can occur in two ways: a) two sulfenyl iodides disproportionate to the disulfide and iodine, or b) the electrophilic S-atom of R-S-I attacks the nucleophilic divalent S-atom of an unchanged R-S-Trt.…”

Section: -60b)mentioning

confidence: 99%

The Synthesis of Cystine Peptides by Iodine Oxidation of S‐Trityl‐cysteine and S‐Acetamidomethyl‐cysteine Peptides

Kamber

Hartmann

Eisler

et al. 1980

Helvetica Chimica Acta

277

171

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SummaryPreviously reported studies of the iodine oxidation of S-trityl-cysteine peptides and S-acetamidomethyl-cysteine peptides, leading directly to cystine peptides, have been extended. Detailed investigations have been made of the reactivities of the S-trityl and the S-acetamidomethyl group towards iodine in various solvents. In chloroform, methylene chloride, trifluoroethanol, and hexafluoroisopropyl alcohol the differences in the reaction rates of the two groups have been found to be extremely large, allowing the selective conversion of the tritylthio groups to disulfides in the presence of the S-acetamidomethyl derivatives. In a second group of solvents, consisting of methanol, acetic acid, dioxane, and mixtures of these solvents with water, simultaneous iodine oxidation of S-trityl-and S-acetamidomethyl-cysteine peptides leads to a preferential combination of these two residues, resulting in predominantly asymmetrical cystine derivatives. -The suitability of the two sulfur-protecting groups in the synthesis of cyclic cystine peptides has been assessed. -Possible reaction mechanisms are discussed. -The scope and limitations of iodine oxidation in peptide synthesis have been studied.The applicability of the method has been demonstrated in the preparation of the open-chain asymmetrical cystine peptide 5, the protected somatostatin derivative 17, and the A(l-13) segment 19 of human insulin, previously employed in the total synthesis of this hormone.Some years ago, we reported that S-trityl-cysteine peptides and S-acetamidomethyl-cysteine peptides [2] could be directly converted into cystine peptides by oxidation with iodine [3] [4]. In the meantime, this method has been applied by us and by others to the synthesis of a variety of structurally different cystine peptides PI ~61. I)Abbreviations are according to the IUPAC-IUB Commission on Biochemical Nomenclature [I]. In addition, the following abbreviations have been adopted in the text: Acm = acetamidomethyl; HFIP= hexafluoroisopropyl alcohol; TFE= trifluoroethanol; DMF = dimethylformamide.

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“…Sulfenyl carboxylates have been implicated recently as intermediates in the disproportionation of unsymmetrical o-carboxyphenyl disulfides (14) and in the overoxidation of 3-carboxymercaptans by iodine (15)(16)(17). The disproportionation of 2-(phenyldithio)benzoic acid to phenyldisulfide and 2,2'-dithiobenzoic acid depends on pH in a manner that suggests that the o-carboxyl group participates in the reaction (14).…”

Section: Resultsmentioning

confidence: 99%

“…The overoxidation of g-carboxymercaptans has been studied by Danehy and his colleagues (15)(16)(17). The normal oxidation of thiols by iodine proceeds with the stoichiomnetry shown in Eq.…”

Section: Resultsmentioning

confidence: 99%

An Adenosine Triphosphate-Phosphate Exchange Catalyzed by a Soluble Enzyme Couple Inhibited by Uncouplers of Oxidative Phosphorylation

Allison

Benitez

1972

Proc. Natl. Acad. Sci. U.S.A.

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The sulfenic acid form of glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12), which is an acyl phosphatase, will catalyze an acetyl phosphate-Pi exchange reaction. This exchange reaction is reversibly inhibited by the uncouplers of oxidative phosphorylation, 2,4-dinitrophenol, m-Cl carbonylcyanide-phenylhydrazone, pentachlorophenol, and 5-chloro-3-tert-butyl-2'-chloro-4'-nitrosalicylanalide, and is irreversibly inhibited by cyanide and dicumarol. An ATP-Pi exchange reaction similar to that catalyzed by mitochondria can be simulated by a system composed of oxidized glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase (EC 2.7 The specific oxidation of the sulfhydryl group at the active site of glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12) (GPD) to a sulfenic acid converts the enzyme ta an acyl phosphatase (1-3). The following reaction scheme has been postulated to account for the hydrolytic reaction catalyzed by the sulfenic-acid form of the enzyme (3):The reaction scleme suggests that the conjugate base of the sulfenic acid reacts with the carbonyl carbon of the acyl phosphate substrate to form an enzyme-sulfenyl carboxylate intermediate with the displacement of inorganic phosphate.In the second step of the reaction scheme, the sulfenyl carboxylate reacts with water to release the carboxylate anion and the regenerated sulfenic acid form of the enzyme. The reaction scheme is consistent with C-O bond cleavage, which Abbreviations: DNP, 2,4-dinitrophenol; mCl-CCPhe, m-Cl carbonylcyanide-phenylhydrazone; 8-13, 5-chloro-3-tert-butyl-2'-chloro-4'..nitrosalicylanalide: GPD, glyceraldehyde-3-phosphate dehydrogenase.

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Oxidation of organic divalent sulfur by iodine. II. Equilibrating thiol-iodine-disulfide-hydrogen iodide system in acetic acid and evidence for sulfenyl iodide intermediates

Cited by 37 publications

References 0 publications

Structural Studies of Cinnamoyl-CoA Reductase and Cinnamyl-Alcohol Dehydrogenase, Key Enzymes of Monolignol Biosynthesis

Structural Studies of Cinnamoyl-CoA Reductase and Cinnamyl-Alcohol Dehydrogenase, Key Enzymes of Monolignol Biosynthesis

The Synthesis of Cystine Peptides by Iodine Oxidation of S‐Trityl‐cysteine and S‐Acetamidomethyl‐cysteine Peptides

An Adenosine Triphosphate-Phosphate Exchange Catalyzed by a Soluble Enzyme Couple Inhibited by Uncouplers of Oxidative Phosphorylation

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