Table 3.

LC-MS/MS analysis of oxidized tryptic peptides of MPO when reacted with hydrogen peroxide. 1.5 μM MPO was reacted with 1.5 mM of hydrogen peroxide in 50 mM phosphate buffer pH 7.4. The reduced and alkylated protein was digested with trypsin and peptides were analyzed by LC-MS/MS. Peptides with a signal ratio of treatment versus control of ⩾3 and a p value of ⩽0.001 are presented.

MPO amino acid #	Identified modified peptide	Oxidized residue on peptide	Charge	m/z Value	Ratio ⩾3 treatment vs control	p-value ⩽0.001	SD
M 85 M 87	SLmFmQWGQLLDHDLDFTPEPAAR	M3 M5	3	950.7812	11.36	1.02E-5	2.75
M 287	KIVGAmVQIITYR	M6	3	503.2933	19.68	1.08E-6	4.59
M 306	DYLPLVLGPTAmR	M12	2	731.3934	6.72	5.99E-10	0.85
M 306	DYLPLVLGPTAmRK	M12	2	795.4401	7.06	0.00016	1.41
M 306	KIVGAMVQIITYRDYLPLVLGPTAmRK	M25	4	766.4382	4.30	1.72E-5	1.06
M 343	YGHTLIQPFmFR	M10	2	763.3850	5.06	8.60E-6	0.42
M 343	YGHTLIQPFmFR	M10	3	509.2593	10.82	3.43E-5	1.46
M 343	IANVFTNAFRYGHTLIQPFmFR	M20	4	665.5958	9.76	1.85E-6	3.00
M 385	GLmATPAKLNR	M3	2	594.3316	9.28	2.38E-5	0.57
M 385	VVLEGGIDPILRGLmATPAKLNR	M15	3	817.1353	36.18	7.90E-6	6.39
M 411	LFEQVmRIGLDLPALNmQR	M6 M17	3	759.4016	13.59	0.000266	2.42
M 422	IGLDLPALNmQR	M10	2	678.8680	7.38	1.00E-5	0.53
M 465 M 478	LmEQYGTPNNIDIWmGGVSEPLKR	M2 M15	3	927.4525	16.01	2.76E-5	4.14