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Characterization of Leukotriene B 4 ‐Omega‐Hydroxylase Activity within Human Polymorphonuclear Granulocytes
Author(s) -
BROM J.,
KÖNIG W.,
STÜNING M.,
RAULF M.,
KÖLLER M.
Publication year - 1987
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1111/j.1365-3083.1987.tb01074.x
Subject(s) - microsome , chemistry , cytochrome , biochemistry , dithionite , leukotriene b4 , enzyme , divalent , zymosan , biology , in vitro , organic chemistry , immunology , inflammation
Human polymorphonuclear granulocytes (PMN) metabolize exogenous [ 3 H]leukotriene B4 (LTB 4 ) into 20‐hydroxy‐ and 20‐carboxy‐[ 3 H]LTB 4 . The conversion was enhanced at acidic pH values (pH 6.0–7.0). Sonication of purified PMN and subcellular fractionation by differential centrifugation showed that major LTB 4 ‐hydroxylase activity was associated with the microsomal fraction (105,000 g pellet). In contrast to intact cells. LTB 4 ‐hydroxylase activity within the microsomal fraction revealed optimal activity at neutral pH and was inhibited by a wide range of divalent cations. There was a strict requirement for the presence of suitable electron donors such as NADPH, Heterocyclic nitrogenous bases, such as imidazole and pyridine, inhibited the LTB 4 , conversion induced by intact PMN as well as by their microsomes. These observations combined with the spectrophotometric analysis (carbon monoxide dithionite‐reduced difference spectrum) supported the assumption that LTB 4 ‐hydroxylase resembled a cytochrome P‐450 enzyme. The LTB 4 ‐hydroxylase within human PMN was not identical with the cytochrome P‐450 of rat liver; hepatic microsomes only showed minute conversion of LTB 4 .