title: Identification and subcellular localization of leukotriene A4-hydrolase activity in human epidermis.
abstract: The purpose of this study was to determine whether normal human epidermis could produce leukotriene B4 (LTB4) from leukotriene A4 (LTA4) ex vivo, and to localize this LTA4-hydrolase activity. Epidermis obtained by suction blister technique incubated with human polymorphonuclear cells, resulted in a 54% increase in LTB4 formation when compared to polymorphonuclear cells incubated alone. Furthermore, human epidermis transformed exogenous LTA4 into LTB4, and this reaction obeyed Michaelis-Menten kinetics with an apparent Km of 6 microM. Subcellular fractionation of homogenized epidermis localized the LTA4-hydrolase activity mainly in the 105,000 x g supernatant fraction (cytoplasmic fraction). This activity was inhibited by two inhibitors of LTA4-hydrolase (bestatin and captopril). Western blot analysis of the 105,000 x g fraction of homogenized epidermis and cultured keratinocytes supported the presence of a LTA4-hydrolase. Thus, normal human epidermis possesses LTA4-hydrolase activity which can transform exogenous LTA4 and polymorphonuclear cell-derived LTA4 into LTB4. The identification of LTA4-hydrolase in the cytoplasmic fraction of human epidermis indicates that epidermal cells may play a more active role in the enzymatic process leading to formation of the proinflammatory compound LTB4 than previously expected.
authors.affiliation: Department of Dermatology, Marselisborg Hospital, University of Aarhus, Denmark.
authors.forename: L
authors.initials: L
authors.lastname: Iversen
authors.forename: V A
authors.initials: VA
authors.lastname: Ziboh
authors.forename: T
authors.initials: T
authors.lastname: Shimizu
authors.forename: N
authors.initials: N
authors.lastname: Ohishi
authors.forename: O
authors.initials: O
authors.lastname: Rådmark
authors.forename: A
authors.initials: A
authors.lastname: Wetterholm
authors.forename: K
authors.initials: K
authors.lastname: Kragballe
mesh_terms: D015153:Blotting, Western; D000001:Calcimycin / Q000494:pharmacology; D004817:Epidermis / Q000378:metabolism*; D004851:Epoxide Hydrolases / Q000378:metabolism*; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D017572:Leukotriene A4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D007975:Leukotriene B4 / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D017572:Leukotriene A4; D007975:Leukotriene B4; D000001:Calcimycin; D009195:Peroxidase; D004851:Epoxide Hydrolases; C043134:leukotriene A4 hydrolase