Lactoperoxidase haem, an iron-porphyrin thiol

Nichol, A. W.; Angel, Lyndall A.; Moon, Therese; Clezy, P. S.

doi:10.1042/bj2470147

Cited by 58 publications

(44 citation statements)

References 12 publications

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“…The non-aligned half- ' # :i: Kimura et al, 1987), human eosinophil peroxidase (hEP, Sakamaki et al, 1989), human myeloperoxidase (hMP, Morishita et al, 1987aj andbovine lactoperoxidase (bLP, this work (Carlstrom, 1969) that bovine lactoperoxidase had no free cysteine. Our results, showing the presence of an odd number of half-cystines, are in accordance with those of Nichol et al (1987), who isolated from reduced bovine lactoperoxidase a protohemin IX thiol and suggested the occurrence of a disulfide bridge between the heme and the peptide chain. Indeed this was the first indication for the presence of a covalent linkage between the heme and the peptide chain.…”

Section: Discussionsupporting

confidence: 92%

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Primary structure of bovine lactoperoxidase, a fourth member of a mammalian heme peroxidase family

Cals¹,

Mailliart²,

Brignon³

et al. 1991

European Journal of Biochemistry

110

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Much is known about bovine lactoperoxidase but no data are available on its primary structure. In this work its main active fraction was isolated from cow's milk and sequenced using a conventional strategy. A clear similarity was found with human myeloperoxidase, eosinophil peroxidase and thyroperoxidase, the sequences of which were recently elucidated from those of their cDNAs and/or genes. The single peptide chain of bovine lactoperoxidase contains 61 2 amino acid residues, including 15 half-cystines and 4 or 5 potential N-glycosylation sites. The corresponding peptide segments of human myeloperoxidase, eosinophil peroxidase and thyroperoxidase display 55%, 54% and 45% identity with bovine lactoperoxidase, respectively, with 14 out of the 15 half-cystines present in each of the four enzymes being located in identical positions. The occurrence of an odd number of halfcystines in bovine lactoperoxidase supports the recent finding of a heme thiol released from this enzyme by a reducing agent, suggesting that the heme is bound to the peptide chain via a disulfide linkage, since the absence of free thiol in the enzyme was reported long ago Closely related heme peroxidases have been detected in most mammalian exocrine secretions. They are believed to protect mucosal surfaces from microorganisms by catalyzing the production of toxic oxidizing agents from HzOz, and halides or SCN-, a pseudohalide. Two of them, bovine lactoperoxidase and human salivary peroxidase, have been especially studied (Tenovuo, 1985). Bovine lactoperoxidase was highly purified and characterized in the early forties (Theorell and Akeson, 1943). Although lactoperoxidase is able to oxidize Br-, I-and SCN-, Reiter and coworkers (1964) demonstrated that oxidation of SCN-was involved in the mechanism of the lactoperoxidase-catalyzed antibacterial effect in bovine milk. Aune and Thomas (1977) and Hoogendoorn et al. (1977) independently concluded that hypothiocyanite (OSCN-) was the main antibacterial species produced from SCN-and H 2 0 z .

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Section: Discussionsupporting

confidence: 92%

“…It was recently shown that the heme was protohemin IX with a mercaptomethyl group replacing a methyl group. This suggested that the protoporphyrin was linked to the peptide chain through a disulfide bridge with a cysteine residue (Nichol et al, 1987). Recently a calcium ion was found to be strongly bound to bovine lactoperoxidase (Booth et al, 1989).…”

mentioning

confidence: 99%

Primary structure of bovine lactoperoxidase, a fourth member of a mammalian heme peroxidase family

Cals¹,

Mailliart²,

Brignon³

et al. 1991

European Journal of Biochemistry

110

View full text Add to dashboard Cite

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“…These studies suggest that the phenyl radical cannot diffuse to the haem iron of LGP as it is probably buried in the protein structure, as in HRP [46,55]. As the haem of LGP cannot be dissociated by standard methods [7,8], we are unable to provide direct evidence on the exact site of interaction of the phenyl radical. However, the loss of Soret absorbance without any detectable shift indicates that the haem environment is modified by the radical.…”

Section: Discussionmentioning

confidence: 83%

“…The enzyme is a single-subunit (82 kDa) glycoprotein of native molecular mass 75 kDa having similarity to LPO. The haem of LGP is tightly bound to the apoenzyme and cannot be dissociated by standard methods [7,8]. The enzyme catalyses the oxidation of SCN − , I − and Br − but not Cl − [6].…”

Section: Introductionmentioning

confidence: 99%

Mechanism-based inactivation of lacrimal-gland peroxidase by phenylhydrazine: a suicidal substrate to probe the active site

Mazumdar

Adak

Chatterjee

et al. 1997

Biochemical Journal

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Humans are exposed to various hydrazine derivatives for therapeutic control of several diseases, and mammalian peroxidases are implicated in the oxidative metabolism of many drugs. The results presented here indicate that lacrimal-gland peroxidase is irreversibly inactivated in a mechanism-based way by phenylhydrazine, which acts as a suicidal substrate in the presence of H # O # . The pseudo-first-order kinetic constants for inactivation at pH 5n5 are K i l 18 µM, k inact l 0n25 min −" and τ &! l 2n75 min, with a second-order rate constant of 0n75i10% M −" :min −" . Approx. 27 mol of phenylhydrazine and 54 mol of H # O # are required per mol of enzyme for complete inactivation. The pHdependent inactivation kinetics indicate the involvement of an ionizable group on the enzyme with a pK a value of 5n4, protonation of which favours inactivation. SCN − , the plausible physiological electron donor of the enzyme, protects it from inactivation. Binding studies by optical difference spectroscopy indicate that phenylhydrazine interacts with the enzyme with a K D value of 60 µM, and its binding is prevented by the presence of SCN − . The enzyme is also protected by 5,5-dimethyl-1-pyrroline N-oxide, a free-radical trap, suggesting the involvement of a radical species in the inactivation. ESR studies indicate the formation of a spin-trapped phenyl radical (a N l 15n9 G and

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“…Lactoperoxidase (LPO 4 ; EC 1.11.1.7) is a Fe 3ϩ heme enzyme that belongs to the mammalian peroxidase family (1). The family of mammalian peroxidases comprises lactoperoxidase (2), eosinophil peroxidase (3), thyroid peroxidase (4), and myeloperoxidase (MPO) (5).…”

mentioning

confidence: 99%