High Dissociation Rate Constant of Ferrous-Dioxy Complex Linked to the Catalase-like Activity in Lactoperoxidase

Galijašević, Semira; Saed, Ghassan M.; Diamond, Michael P.; Abu-Soûd, Husam M.

doi:10.1074/jbc.m406003200

Cited by 18 publications

(17 citation statements)

References 62 publications

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“…Several studies have indicated that this inactivation is, in fact, partially reversible. Ghibaudi and Laurenti (2003) propose that compound-III is able to reduce both compound-I and -II, and Galijasevic, Saed, Diamond, and Abu-Soud (2004) provide data that support the notion that compound-III can be formed during steady-state catalysis and suggest that the role of its formation and decay is the removal of an excess of hydrogen peroxide. Another mechanism by which a peroxidase removes excess amounts of hydrogen peroxide is catalase activity.…”

Section: Biochemistry and Mechanism Of Lactoperoxidasementioning

confidence: 75%

Lactoperoxidase: From catalytic mechanism to practical applications

Boots¹,

Floris

2006

International Dairy Journal

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Section: Biochemistry and Mechanism Of Lactoperoxidasementioning

confidence: 75%

Lactoperoxidase: From catalytic mechanism to practical applications

Boots¹,

Floris

2006

International Dairy Journal

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“…Purity of isolated MPO was established by demonstrating a Reinheitzhal (RZ) value of >0.85 (A 430 /A 280 ), SDS PAGE analysis was achieved with Coomassie blue staining, and in-gel tetramethylbenzidine peroxidase staining to confirm absence of observable contaminating eosinophil peroxidase activity [45]. Enzyme concentration was determined spectrophotometrically utilizing extinction coefficients of 89,000 M −1 cm −1 /heme of MPO [46]. …”

Section: Enzyme Purificationmentioning

confidence: 99%

“…Experiments were initially performed under conditions identical to those recently reported for MPO and other related hemoproteins to facilitate comparison [46][47][48]. Measurements were carried out under an aerobic atmosphere at 10 °C following rapid mixing of equal volumes of an H 2 O 2 -containing buffer solution and a peroxidase solution that contained 100 mM Cl − and/ or different Trp concentrations.…”

Section: Rapid Kinetic Measurementsmentioning

confidence: 99%

Potential role of tryptophan and chloride in the inhibition of human myeloperoxidase

Galijašević

Abdulhamid

Abu-Soûd

2008

Free Radical Biology and Medicine

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Myeloperoxidase (MPO) binds H 2 O 2 in the absence and presence of chloride (Cl − ) and catalyzes the formation of potent oxidants through 1e − and 2e − oxidation pathways. These potent oxidants have been implicated in the pathogenesis of various diseases including atherosclerosis, asthma, arthritis, and cancer. Thus, inhibition of MPO and its byproducts may have a much wide application in biological systems. Using direct rapid kinetic measurements and H 2 O 2 -selective electrodes, we showed that tryptophan (Trp), an essential amino acid, was linked kinetically to the inhibition of MPO catalysis under physiological-like conditions. Trp inactivated MPO in the absence and presence of plasma levels of chloride (Cl − ), in various degrees, through binding to MPO forming the inactive complexes, Trp-MPO and Trp-MPO-Cl, respectively; and accelerating MPO Compound II formation, an inactive form of MPO. Inactivation of MPO was mirrored by the direct conversion of MPO-Fe(III) to MPO Compound II without any sign of Compound I accumulation. This behavior indicates that Trp binding modulates the formation of MPO intermediates and their decay rates. Importantly, Trp is a poor substrate for MPO Compound II and has no role in destabilizing complex formation. Thus, the overall MPO catalytic activity will be limited by: 1) the dissociation of Trp from Trp-MPO and Trp-MPO-Cl complexes; 2) the affinity of MPO Compound I towards Cl − versus Trp; and 3) the slow conversion of MPO Compound II to MPO-Fe(III). Importantly, Trp dependentinhibition of MPO occurred with a wide range of concentrations that span various physiological and supplemental ranges.

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“…The amount of MLT used (100 μM) in the current work is sufficient to inhibit MPO. Studies on the effect of MLT on HOCl production by neutrophils and purified MPO have showed that the concentration of MLT that inhibited HOCl production by 50% (IC 50 ) was estimated to be 18 μM and reduced to 4 μM when superoxide was removed by addition of superoxide dismutase [52]. In contrast, the IC 50 value, calculated from the initial rate of H 2 O 2 consumption as a function of the MLT concentration was 3 μM [17].…”

Section: Discussionmentioning

confidence: 99%