Sulphydryl Oxidase: Oxidation of Sulphydryl Groups and the Formation of Three‐Dimensional Structure in Proteins

Swaisgood, Harold E.; Horton, Helen

doi:10.1002/9780470720554.ch13

Cited by 5 publications

(2 citation statements)

References 23 publications

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“…The first is the substrate specificity pattern shown by un-fractionated skim milk. The earlier work reported that DTT was not a substrate of the milk sulfhydryl oxidase either in skim milk or in a purified form (13,15,20,44). However, under the conditions of Figure 1, DTT is a better substrate than GSH (∼1.5-fold) in skim milk.…”

Section: Sulfhydryl Oxidase Activity In Skim Milkmentioning

confidence: 85%

A Flavin-Dependent Sulfhydryl Oxidase in Bovine Milk

et al. 2007

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Both metal and flavin-dependent sulfhydryl oxidases catalyze the net generation of disulfide bonds with the reduction of oxygen to hydrogen peroxide. The first mammalian sulfhydryl oxidase to be described was an iron-dependent enzyme isolated from bovine milk whey (Janolino, V.G., and Swaisgood, H.E. (1975) J. Biol. Chem. 250, 2532-2537). This protein was reported to contain 0.5 atoms of iron per 89 kDa subunit and to be completely inhibited by ethylenediaminetetraacetate (EDTA). However the present work shows that a soluble 62 kDa FAD-linked and EDTA-insensitive sulfhydryl oxidase apparently constitutes the dominant disulfide bond-generating activity in skim milk. Unlike the metalloenzyme, the flavoprotein is not associated tightly with skim milk membranes. Sequencing of the purified bovine enzyme (>70% coverage) showed it to be a member of the Quiescin-sulfhydryl oxidase (QSOX) family. Consistent with its solubility, this bovine QSOX1 paralogue lacks the C-terminal transmembrane span of the long form of these proteins. Bovine milk QSOX1 is highly active toward reduced RNase and with the model substrate dithiothreitol. The significance of these new findings is discussed in relation to the earlier reports of metal-dependent sulfhydryl oxidases.

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Section: Sulfhydryl Oxidase Activity In Skim Milkmentioning

confidence: 85%

A Flavin-Dependent Sulfhydryl Oxidase in Bovine Milk

et al. 2007

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“…The name "sulfhydryl oxidase" was first coined by Kiermeier and coworkers [1,2] to describe an activity in fresh milk that counteracts the undesirable "burnt" flavors associated with ultrahigh temperature pasteurization [3]. This reaction involves the generation of disulfide bonds between cysteine residues of denatured globular proteins [4]: (1) This first mammalian sulfhydryl oxidase has been extensively studied by Swaisgood and coworkers [3][4][5][6][7] and is reported to be an iron-dependent enzyme capable of oxidizing both glutathione and protein thiol groups. Subsequently, a number of metalloenzyme sulfhydryl oxidases have been shown to contain either iron [4,8,9] or copper [10][11][12].…”

Section: Introduction To Sulfhydryl Oxidasesmentioning

confidence: 99%

Generating disulfides with the Quiescin-sulfhydryl oxidases

Heckler

Rancy

Kodali

et al. 2008

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research

113

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The Quiescin-sulfhydryl oxidase (QSOX) family of flavoenzymes catalyzes the direct and facile insertion of disulfide bonds into unfolded reduced proteins with concomitant reduction of oxygen to hydrogen peroxide. This review discusses the chemical mechanism of these enzymes and the involvement of thioredoxin and flavin-binding domains in catalysis. The variability of CxxC motifs in the QSOX family is highlighted and attention is drawn to the steric factors that may promote efficient thiol/disulfide exchange during oxidative protein folding. The varied cellular location of these multi-domain sulfhydryl oxidases is reviewed and potential intracellular and extracellular roles are summarized. Finally, this review identifies important unresolved questions concerning this ancient family of sulfhydryl oxidases.

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Indigenous Milk Enzymes

Kitchen

1985

Developments in Dairy Chemistry—3

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Sulphydryl Oxidase: Oxidation of Sulphydryl Groups and the Formation of Three‐Dimensional Structure in Proteins

Cited by 5 publications

References 23 publications

A Flavin-Dependent Sulfhydryl Oxidase in Bovine Milk

A Flavin-Dependent Sulfhydryl Oxidase in Bovine Milk

Generating disulfides with the Quiescin-sulfhydryl oxidases

Indigenous Milk Enzymes

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