Chlorination of N-acetyltyrosine with HOCl, chloramines, and myeloperoxidase-hydrogen peroxide-chloride system

• Autorzy: Drabik G. , Naskalski J.W.
• Języki publikacji: EN

Abstrakty

EN

N-acetyl-L-tyrosine (N-acTyr), with the alpha amine residue blocked by acetylation, can mimic the reactivity of exposed tyrosyl residues incorporated into polypeptides. In this study chlorination of N-acTyr residue at positions 3 and 5 in reactions with NaOCl, chlor­amines and the myeloperoxidase (MPO)-H2O2-Cl- chlorinating system were invesigated. The reaction of N-acTyr with HOCl/OCl depends on the reactant concentration ratio em­ployed. At the OCl-/N-acTyr (molar) ratio 1:4 and pH 5.0 the chlorination reaction yield is about 96% and 3-chlorotyrosine is the predominant reaction product. At the OCl-/ N-acTyr molar ratio 1: 1.1 both 3-chlorotyrosine and 3,5-dichlorotyrosine are formed. The yield of tyrosine chlorination depends also on pH, amounting to 100% at pH 5.5,91% at pH 4.5 and 66% at pH 3.0. Replacing HOCl/OCl- by leucine/chloramine or alanine/chlora- mine in the reaction system, at pH 4.5 and 7.4, produces trace amount of 3-chlorotyrosine with the reaction yield of about 2% only. Employing the MPO-H2O2-O chlorinating sys­tem at pH 5.4, production of a small amount of N-acTyr 3-chloroderivative was observed, but the reaction yield was low due to the rapid inactivation of MPO in the reaction system. The study results indicate that direct chlorination of tyrosyl residues which are not incor­porated into the polypeptide structure occurs with excess HOCl/OCl- in acidic media. Due to the inability of the myeloperoxidase-H2O2-Cl system to produce high enough HOCl concentrations, the MPO-mediated tyrosyl residue chlorination is not effective. Semistable amino-acid chloramines also appeared not effective as chlorine donors in di­rect tyrosyl chlorination.

Słowa kluczowe

EN

hypochlorite; tyrosine chloroderivative; N-acetyltyrosine; myeloperoxidase-hydrogen peroxide-chloride system; chloramine; chlorination

• Wydawca: -
• Czasopismo: Acta Biochimica Polonica
• Rocznik: 2001
• Tom: 48
• Numer: 1
• Opis fizyczny: p.271-275,fig.

Twórcy

autor

Drabik G.

• Collegium Medicum, Jagiellonian University, Krakow, Poland

autor

Naskalski J.W.

Bibliografia

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