Oxidation of thiocyanate to cyanide and sulfate by the lactoperoxidase-hydrogen peroxide system

Chung, Joaquín; Wood, John L.

doi:10.1016/0003-9861(70)90108-6

Cited by 53 publications

(25 citation statements)

References 24 publications

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“…The oxidation of thiocyanate proceeds as follows. First, thiocyanate is hydrolyzed to cyanate (OCN − ) and sulfide, followed by hydrolysis of cyanate to ammonia and bicarbonate and oxidation of sulfide to sulfate (Chung and Wood, 1970;Happold et al, 1954;Youatt, 1954). Oxidation of thiocyanate by a mixed, activated sludge-derived microbial population was achieved in a previous study (Hung and Pavlostathis, 1997), which confirmed the aforementioned pathway and assessed the effect of thiocyanate on the activated sludge process.…”

Section: Introductionmentioning

confidence: 84%

Kinetics and modeling of autotrophic thiocyanate biodegradation

Hung

Pavlostathis

1999

Biotechnol. Bioeng.

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Section: Introductionmentioning

confidence: 84%

Kinetics and modeling of autotrophic thiocyanate biodegradation

Hung

Pavlostathis

1999

Biotechnol. Bioeng.

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“…One electron oxidation of SCN − yields unstable thiocyanate radical, which then dimerizes to generate a labile short-lived intermediate, thiocyanogen (SCN) 2 [63], [64]. The resulting (SCN) 2 is rapidly hydrolyzed to generate either HOSCN/OSCN − or CN − without the formation of HOSCN as an end product [61], [63], [65], [66]. Alternatively, SCN − can react directly with HOCl to generate HOSCN [67].…”

Section: Discussionmentioning

confidence: 99%

Hypochlorous Acid-Induced Heme Degradation from Lactoperoxidase as a Novel Mechanism of Free Iron Release and Tissue Injury in Inflammatory Diseases

et al. 2011

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Lactoperoxidase (LPO) is the major consumer of hydrogen peroxide (H2O2) in the airways through its ability to oxidize thiocyanate (SCN−) to produce hypothiocyanous acid, an antimicrobial agent. In nasal inflammatory diseases, such as cystic fibrosis, both LPO and myeloperoxidase (MPO), another mammalian peroxidase secreted by neutrophils, are known to co-localize. The aim of this study was to assess the interaction of LPO and hypochlorous acid (HOCl), the final product of MPO. Our rapid kinetic measurements revealed that HOCl binds rapidly and reversibly to LPO-Fe(III) to form the LPO-Fe(III)-OCl complex, which in turn decayed irreversibly to LPO Compound II through the formation of Compound I. The decay rate constant of Compound II decreased with increasing HOCl concentration with an inflection point at 100 µM HOCl, after which the decay rate increased. This point of inflection is the critical concentration of HOCl beyond which HOCl switches its role, from mediating destabilization of LPO Compound II to LPO heme destruction. Lactoperoxidase heme destruction was associated with protein aggregation, free iron release, and formation of a number of fluorescent heme degradation products. Similar results were obtained when LPO-Fe(II)-O2, Compound III, was exposed to HOCl. Heme destruction can be partially or completely prevented in the presence of SCN−. On the basis of the present results we concluded that a complex bi-directional relationship exists between LPO activity and HOCl levels at sites of inflammation; LPO serve as a catalytic sink for HOCl, while HOCl serves to modulate LPO catalytic activity, bioavailability, and function.

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“…Sulfate, sulfite, cyanate, cyanide, carbonate, and ammonia have been postulated as products of the chemical or the enzymic oxidation of thiocyanate by hydrogen peroxide (12,15,27,38). These substances were not toxic to P. anaerobius at a concentration of 0.1 mM, and they did not potentiate the bactericidal effect of 80 ,uM hydrogen peroxide (data not shown).…”

mentioning

confidence: 99%

Bactericidal and cytotoxic effects of hypothiocyanite-hydrogen peroxide mixtures

Carlsson¹,

Edlund²,

Hänström³

1984

Infect Immun

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Lactoperoxidase catalyzes the oxidation of thiocyanate by hydrogen peroxide into hypothiocyanite, a reaction which can protect bacterial and mammalian cells from killing by hydrogen peroxide. The present study demonstrates, however, that lactoperoxidase in the presence of thiocyanate can actually potentiate the bactericidal and cytotoxic effects of hydrogen peroxide under specific conditions, such as when hydrogen peroxide is present in the reaction mixtures in excess of thiocyanate. The toxic agent was also formed in the absence of lactoperoxidase in a reaction between hypothiocyanite and hydrogen peroxide. Sulfate, sulfite, cyanate, carbonate, and ammonia, which have been postulated to be formed in the chemical oxidation of hypothiocyanite by hydrogen peroxide, were not bactericidal and did not potentiate the bactericidal effect of hydrogen peroxide. Cyanosulfurous acid, the only other postulated product of the chemical oxidation of hypothiocyanite by hydrogen peroxide, may be the killing agent.

show abstract

Oxidation of thiocyanate to cyanide and sulfate by the lactoperoxidase-hydrogen peroxide system

Cited by 53 publications

References 24 publications

Kinetics and modeling of autotrophic thiocyanate biodegradation

Kinetics and modeling of autotrophic thiocyanate biodegradation

Hypochlorous Acid-Induced Heme Degradation from Lactoperoxidase as a Novel Mechanism of Free Iron Release and Tissue Injury in Inflammatory Diseases

Bactericidal and cytotoxic effects of hypothiocyanite-hydrogen peroxide mixtures

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