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A transient kinetic study on the reactivity of recombinant unprocessed monomeric myeloperoxidase
Author(s) -
Furtmüller Paul Georg,
Jantschko Walter,
Regelsberger Günther,
Jakopitsch Christa,
Moguilevsky Nicole,
Obinger Christian
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02725-9
Subject(s) - chemistry , ferric , myeloperoxidase , bromide , enzyme , stereochemistry , thiocyanate , hydrogen peroxide , chinese hamster ovary cell , redox , iodide , medicinal chemistry , biochemistry , inorganic chemistry , biology , receptor , immunology , inflammation
Spectral and kinetic features of the redox intermediates of human recombinant unprocessed monomeric myeloperoxidase (recMPO), purified from an engineered Chinese hamster ovary cell line, were studied by the multi‐mixing stopped‐flow technique. Both the ferric protein and compounds I and II showed essentially the same kinetic behavior as the mature dimeric protein (MPO) isolated from polymorphonuclear leukocytes. Firstly, hydrogen peroxide mediated both oxidation of ferric recMPO to compound I (1.9×10 7 M −1 s −1 , pH 7 and 15°C) and reduction of compound I to compound II (3.0×10 4 M −1 s −1 , pH 7 and 15°C). With chloride, bromide, iodide and thiocyanate compound I was reduced back to the ferric enzyme (3.6×10 4 M −1 s −1 , 1.4×10 6 M −1 s −1 , 1.4×10 7 M −1 s −1 and 1.4×10 7 M −1 s −1 , respectively), whereas the endogenous one‐electron donor ascorbate mediated transformation of compound I to compound II (2.3×10 5 M −1 s −1 ) and of compound II back to the resting enzyme (5.0×10 3 M −1 s −1 ). Comparing the data of this study with those known from the mature enzyme strongly suggests that the processing of the precursor enzyme (recMPO) into the mature form occurs without structural changes at the active site and that the subunits in the mature dimeric enzyme work independently.