Measured by its ability to oxidize guaiacol in the presence of hydrogen peroxide. Capeillere-Blandin, C. (1998) Biochem J. 336 :395. The specific activity is >8,000 pmol/min/μg, as measured under the described conditions.
Mouse myeloma cell line, NS0-derived mouse Myeloperoxidase/MPO protein Met16-Thr718, with a C-terminal 10-His tag
>90%, by SDS-PAGE visualized with Silver Staining and quantitative densitometry by Coomassie® Blue Staining.
<1.0 EU per 1 μg of the protein by the LAL method.
81 kDa. Disclaimer note: The observed molecular weight of the protein may vary from the listed predicted molecular weight due to post translational modifications, post translation cleavages, relative charges, and other experimental factors.
Quartz Cuvette (Starna Cells, Catalog # 9B-Q-10) or equivalent
Spectrophotometer with cuvette port (Model: Spectramax Plus by Molecular Devices) or equivalent
Prepare the substrate mixture by diluting guaiacol to 100 mM in Assay Buffer containing 0.0034% H2O2.
Shake or stir for 15 minutes at room temperature. Protect from light.
Dilute rmMPO to 3.34 µg/mL in Assay Buffer.
Load into a quartz cuvette 400 µL of 3.34 µg/mL rmMPO and start the reaction by adding 400 µL of the diluted guaiacol/H2O2 mixture. As a Substrate Blank combine 400 µL of Assay Buffer and 400 µL of the diluted guaiacol/H2O2 mixture (note: it is essential to monitor the reaction immediately after the introduction of the substrate mixture).
Read each cuvette at 470 nm in kinetic mode for 1 minute. Use only the first 10 seconds of data in the activity calculation.
Calculate specific activity:
Specific Activity (pmol/min/µg) =
Absorbance change per minute ( delta A/min) x sample volume (L) x 1012 pmol/mol
ext. coeff (M-1cm-1) x amount of enzyme (µg)
Notes: Absorbance readings are adjusted for the Substrate Blank Use an extinction coefficient of 5580 M-1cm-1 The output of many spectrophotometers is in milli absorbance units per minute in kinetic mode Per Reaction:
rmMPO: 1.336 μg (20 nM)
H2O2: 0.0017% (0.5 mM)
Guaiacol: 50 mM
This product is produced by and ships from R&D Systems, Inc., a Bio-Techne brand.
Alternate Names for Recombinant Mouse Myeloperoxidase Protein, CF
Myeloperoxidase (MPO) is a heme‑containing enzyme belonging to the XPO subfamily of peroxidases. It is an abundant neutrophil and monocyte glycoprotein that catalyzes the hydrogen peroxide‑dependent conversion of chloride, bromide, and iodide to multiple reactive species (1). Post‑translational processing of human MPO involves the insertion of a heme moiety and the proteolytic removal of both a propeptide and a 6 aa internal peptide (2). This results in a disulfide‑linked dimer composed of a 60 kDa heavy and 12 kDa light chain that associate into a 150 kDa enzymatically active tetramer. The tetramer contains two heme groups and one disulfide bond between the heavy chains (2). Mouse and human MPO share 87% aa sequence identity. MPO activity results in protein nitrosylation and the formation of 3‑chlorotyrosine and dityrosine crosslinks (4‑6). Modification of ApoB100, as well as the lipid and cholesterol components of LDL and HDL, promotes the development of atherosclerosis (5, 7‑9). MPO is also associated with a variety of other diseases (1), and inhibits vasodilation in inflammation by depleting the levels of NO (10). Serum albumin functions as a carrier protein during MPO movement to the basolateral side of epithelial cells (11). MPO is stored in neutrophil azurophilic granules. Upon cellular activation, it is deposited into pathogen‑containing phagosomes (2). While mice lacking MPO are impaired in clearing select microbial infections, MPO deficiency in humans does not necessarily result in heightened susceptibility to infections (12, 13).
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Hazen, S.L. and J.W. Heinecke (1997) J. Clin. Invest. 99:2075.
Heinecke, J.W. et al. (1993) J. Clin. Invest. 91:2866.
Podrez, E.A. et al. (1999) J. Clin. Invest. 103:1547.
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Hazen, S.L. et al. (1996) J. Biol. Chem. 271:23080.
Eiserich, J.P. et al. (2002) Science 296:2391.
Tiruppathi, C. et al. (2004) Proc. Natl. Acad. Sci. 101:7699.
Aratani Y. et al. (2000) J. Infect. Dis. 182:1276.
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