An alternative view of the proposed alternative activities of hemopexin |
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Authors: | Mauk Marcia R Smith Ann Mauk A Grant |
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Affiliation: | 1Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3;2Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-K.C., Kansas City, Missouri 64110 |
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Abstract: | Hemopexin is a plasma protein that plays a well-established biological role in sequestering heme that is released into the plasma from hemoglobin and myoglobin as the result of intravascular or extravascular hemolysis as well as from skeletal muscle trauma or neuromuscular disease. In recent years, a variety of additional biological activities have been attributed to hemopexin, for example, hyaluronidase activity, serine protease activity, pro-inflammatory and anti-inflammatory activity as well as suppression of lymphocyte necrosis, inhibition of cellular adhesion, and binding of divalent metal ions. This review examines the challenges involved in the purification of hemopexin from plasma and in the recombinant expression of hemopexin and evaluates the questions that these challenges and the characteristics of hemopexin raise concerning the validity of many of the new activities proposed for this protein. As well, an homology model of the three-dimensional structure of human hemopexin is used to reveal that the protein lacks the catalytic triad that is characteristic of many serine proteases but that hemopexin possesses two highly exposed Arg-Gly-Glu sequences that may promote interaction with cell surfaces. |
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Keywords: | hemopexin serine protease anti-inflammatory pro-inflammatory lymphocyte necrosis factor metal ion binding cell adhesion heme binding |
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