The 150-kDa MPO protein is a dimer consisting of two 15-kDa light chains and two variable-weight glycosylated heavy chains bound to a prosthetic heme group. Three isoforms have been identified, differing only in the size of the heavy chains. It contains a calcium binding site with seven ligands, forming a pentagonal pyramid conformation. One of the ligands is the carbonyl group of Asp 96. Calcium-binding is important for structure of the active site because of Asp 96's close proximity to the catalytic His95 side chain.
Recent studies have reported an association between elevated myeloperoxidase levels and the severity of coronary artery disease. And Heslop et al. reported that elevated MPO levels more than doubled the risk for cardiovascular mortality over a 13-year period. It has also been suggested that myeloperoxidase plays a significant role in the development of the atherosclerotic lesion and rendering plaques unstable.
An initial 2003 study suggested that MPO could serve as a sensitive predictor for myocardial infarction in patients presenting with chest pain. Since then, there have been over 100 published studies documenting the utility of MPO testing. The 2010 Heslop et al. study reported that measuring both MPO and CRP (C-reactive protein; a general and cardiac-related marker of inflammation) provided added benefit for risk prediction than just measuring CRP alone.
Myeloperoxidase is the first and so far only human enzyme known to break down carbon nanotubes, allaying a concern among clinicians that using nanotubes for targeted delivery of medicines would lead to an unhealthy buildup of nanotubes in tissues.
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^ abHeslop CL, Frohlich JJ, Hill JS (March 2010). "Myeloperoxidase and C-reactive protein have combined utility for long-term prediction of cardiovascular mortality after coronary angiography". J. Am. Coll. Cardiol.55 (11): 1102–9. doi:10.1016/j.jacc.2009.11.050. PMID20223364.
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^Kagan VE, Konduru NV, Feng W, Allen BL, Conroy J, Volkov Y, Vlasova II, Belikova NA, Yanamala N, Kapralov A, Tyurina YY, Shi J, Kisin ER, Murray AR, Franks J, Stolz D, Gou P, Klein-Seetharaman J, Fadeel B, Star A, Shvedova AA (April 2010). "Carbon nanotubes degraded by neutrophil myeloperoxidase induce less pulmonary inflammation". Nat Nanotechnol5 (5): 354–9. doi:10.1038/nnano.2010.44. PMID20364135. Lay summary – popsci.com.