Oxidation Processes. XVI.<sup>1</sup> The Autoxidation of Ascorbic Acid

Weißberger, A.; LuValle, James E.; Thomas, D. S.

doi:10.1021/ja01250a038

Cited by 114 publications

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“…Although we diluted the purified stock enzyme 300 times with buffer, it might still have contained about 5 pM DL-dithiothreitol, which might be sufficient to prevent enzyme inactivation by AsA at low concentration for a short period of time (see below). AsA is known to be rapidly autoxidized at pH 7.2 or more [26], pH values at which dehydroascorbic acid and various active oxygen species, such as hydrogen peroxide (H202), superoxide (O;), singlet oxygen (lo2), and the hydroxyl radical (OH') are formed [12], and these active species have been shown to inactivate several enzymes [lo, 11, 14, 171. Thus we examined whether these species were responsible for inactivation of acetyl-CoA hydrolase by AsA.…”

Section: Resultsmentioning

confidence: 99%

Oxidative inactivation of an extramitochondrial acetyl-CoA hydrolase by autoxidation of l-ascorbic acid

et al. 1985

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The activity of acetyl-CoA hydrolase (dimeric form) purified from the supernatant fraction of rat liver was shown to have a half-life ( t 1 / 2 ) of 3 min at 0"C, but to be stable at 3 7 T (t1/2 = 34 h) Biochemistry 22, 584-5901, Incubation of the purified enzyme with L-ascorbic acid (AsA) at 3 7~' C resulted in inactivation of the enzyme ( t l j z = 90 min at 2 mM AsA). The extent of inactivation was greatly enhanced by addition of transition metal ions (Cu2+, Fez', and Fe3+). Thiol reducing agents, such as reduced glutathione and rx-dithiothreitol, protected the hydrolase from inactivation by AsA. However, these materials did not restore the catalytic activity of the enzyme inactivated by AsA. When AsA solution containing Cuz+ was preincubated under aerobic conditions at 37°C for various times in the absence of enzyme, and then aliquots were incubated with the enzyme solution for 20 min, remaining activity was found to decrease with incrcase in the preincubation time, reaching a minimum at 60 min. However, further preincubation reduced the potential for inactivation. Catalase, a hydrogen peroxide ( H 2 0 2 ) scavenger, almost completely prevented inactivation of the enzyme by AsA plus Cu2+. Superoxide dismutase and tiron, which are both superoxide (0;) scavengers, also prevented inactivation of the enzyme. A high concentration of mannitol, a hydroxyl radical (OH') scavenger, partially protected the enzyme from inactivation. These results suggest that inactivation of the enzyme by AsA in the presence of Cu2+ was due to the effect of active oxygen species ( H z 0 2 , O;, OH') that are known to be autoxidation products of AsA. Valeryl-CoA, a competitive inhibitor of acetyl-CoA hydrolase, greatly protected the enzyme from inactivation by AsA plus CU", but ATP and ADP, which are both effectors ofthis enzyme, had only slight protective effects. These results suggest that inactivation of this enzyme by addition of AsA plus Cu2+ was mainly due to attack on its active site.Acetyl-CoA hydrolase has been found in a wide variety of tissues of many species [l -51. In rats, extramitochondrial acetyl-CoA hydrolase is extremely labile in a liver homogenate [5] as well as in excised liver [6] prepared a t low temperature. The enzyme purified from the supernatant fraction of rat liver is activated by ATP and completely inhibited by ADP [5] and has various forms (tetramer, dimer and monomer) [7]. In the presence of ATP or ADP, but not AMP, at room temperature, the dimeric form ( M , 135000) of the enzyme reassociates to the tetraineric form ( M , 240000) and removal of nucleotides from the tetrameric enzyme causes its dissociation, mainly into the enzymatically active dimeric form and partly into the inactive monomeric form [7]. Formation of the monomer is greater when the dimeric and tetrameric forms are treated at low temperature [7]. Nucleotides, various acyl-CoA derivatives, CoASH, polyols and a high concentration of salt afford partial or complete protection of the enzyme against inactivation or dissociation by cold [8]....

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Section: Resultsmentioning

confidence: 99%

Oxidative inactivation of an extramitochondrial acetyl-CoA hydrolase by autoxidation of l-ascorbic acid

et al. 1985

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“…Steinman and Dawson (24) reinvestigated this alleged formation of H202, and proved conclusively that H20 and not H202 was an end product of this oxidation. The aerobic oxidation of ascorbic acid as catalyzed by copper ion results in the formation of H202 as an end product (9,31,32). Indirect evidence, supplied from three independent approaches to the problem, point to the production of H202 as an end product of the enzymatic oxidation of ascorbic acid in Physarum.…”

Section: Literature Citedmentioning

confidence: 99%

The Enzymatic Oxidation of Ascorbic Acid in the Slime Mold, Physarum Polycephalum.

Ward

1955

Plant Physiol.

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“…In continuation of previous study [15] where the effect of N-acetyl-L-cysteine (NAC) on HA degradation due to Weisberger biogenic oxidative system (WBOS) [16,17] comprising ascorbic acid plus Cu(II) ions was examined, this study was aimed at the modifications in HA macromolecules exposed to the WBOS in the absence and presence of bucillamine N-(2-mercapto-2-methylpropionyl)-L-cysteine ( Figure 1b). Bucillamine was supposed to be significantly more efficient antioxidant than the parent NAC.…”

Section: Introductionmentioning

confidence: 99%

Effect of Bucillamine on Free-Radical-Mediated Degradation of High-Molar-Mass Hyaluronan Induced in vitro by Ascorbic Acid and Cu(II) Ions

et al. 2014

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Abstract:The bucillamine effect on free-radical-mediated degradation of high-molar-mass hyaluronan (HA) has been elucidated. As HA fragmentation is expected to decrease its dynamic viscosity, rotational viscometry was applied to follow the oxidative HA degradation. Non-isothermal chemiluminometry, thermogravimetry, differential scanning calorimetry, and size-exclusion chromatography (SEC) were applied to characterize resulting HA fragments. Although bucillamine completely inhibited the HA viscosity decrease caused by oxidative system, indicating HA protection from degradation, SEC analysis suggested that some other mechanisms leading to the bucillamine transformations without the decay of the viscosity may come into a play as well. Nonetheless, the link between the reduction of OPEN ACCESSPolymers 2014, 6 2626 chemiluminescence intensity and disappearance of the differential scanning calorimetry exotherm at 270 °C for fragmented HAs indicates a particular role of the bucillamine in preventing the decrease of HA viscosity.

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Oxidation Processes. XVI.¹ The Autoxidation of Ascorbic Acid

Cited by 114 publications

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Oxidative inactivation of an extramitochondrial acetyl-CoA hydrolase by autoxidation of l-ascorbic acid

Oxidative inactivation of an extramitochondrial acetyl-CoA hydrolase by autoxidation of l-ascorbic acid

The Enzymatic Oxidation of Ascorbic Acid in the Slime Mold, Physarum Polycephalum.

Effect of Bucillamine on Free-Radical-Mediated Degradation of High-Molar-Mass Hyaluronan Induced in vitro by Ascorbic Acid and Cu(II) Ions

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Oxidation Processes. XVI.1 The Autoxidation of Ascorbic Acid

Cited by 114 publications

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Oxidative inactivation of an extramitochondrial acetyl-CoA hydrolase by autoxidation of l-ascorbic acid

Oxidative inactivation of an extramitochondrial acetyl-CoA hydrolase by autoxidation of l-ascorbic acid

The Enzymatic Oxidation of Ascorbic Acid in the Slime Mold, Physarum Polycephalum.

Effect of Bucillamine on Free-Radical-Mediated Degradation of High-Molar-Mass Hyaluronan Induced in vitro by Ascorbic Acid and Cu(II) Ions

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Oxidation Processes. XVI.¹ The Autoxidation of Ascorbic Acid