Isolation and Identification of a Protoheme IX Derivative Released During Autolytic Cleavage of Human Myeloperoxidase

Taylor, K L; Strobel, Frank W.; Yue, Kwok To; Ram, Preetha; Pohl, Jan; Woods, Amina S.; Kinkade, Joseph M.

doi:10.1006/abbi.1995.1083

Cited by 51 publications

(56 citation statements)

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“…This was taken as proof for the presence of an aldehyde group (8). The presence of the sulfonium ion linkage, however, offers a reasonable explanation for the reactivity with these carbonyl reagents (16). It should be noted that also photochemically modified myeloperoxidase has spectra similar to those of the Met 243 mutants (43).…”

Section: Discussionmentioning

confidence: 97%

“…Taylor et al (16) state that the contribution of the electrophilic sulfonium ion linkage to the red shift of the Soret maximum of the native oxidized enzyme would be small. We have shown that this is not the case; when this linkage is broken through mutation of Met 243 a blue shift of up to 18 nm occurs, which is even larger in the reduced state.…”

Section: Discussionmentioning

confidence: 99%

“…Based on the unique autocleavage Met 243--Pro 244 site of MPO, resembling the cyanogen bromide dependent-cleavage of Met-X bonds, and the fact that Met 243 is in close proximity to the prosthetic group of MPO, Taylor et al (15) proposed that Met 243 was involved in a sulfonium ion linkage to the heme group. Later studies showed that this sulfonium ion linkage involved the vinyl group of pyrrole ring A (13,16). Met 243 is replaced by a threonine in human EPO (10), whereas in bovine LPO a glutamine is found at this position (17), and, as recently shown by Ueda et al (11), in human LPO a histidine is present.…”

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confidence: 95%

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The Sulfonium Ion Linkage in Myeloperoxidase

Kooter¹,

Moguilevsky²,

Bollen³

et al. 1999

Journal of Biological Chemistry

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The heme group of myeloperoxidase is covalently linked via two ester bonds to the protein and a unique sulfonium ion linkage involving Met 243 . Mutation of Met 243 into Thr, Gln, and Val, which are the corresponding residues of eosinophil peroxidase, lactoperoxidase, and thyroid peroxidase, respectively, and into Cys was performed. The Soret band in the optical absorbance spectrum in the oxidized mutants is now found at approximately 411 nm. Both the pyridine hemochrome spectra and resonance Raman spectra of the mutants are affected by the mutation. In the Met 243 mutants the affinity for chloride has decreased 100-fold. All mutants have lost their chlorination activity, except for the M243T mutant, which still has 15% activity left. By Fourier transform infared difference spectroscopy it was possible to specifically detect the 13 CD 3 -labeled methionyl sulfonium ion linkage. We conclude that the sulfonium ion linkage serves two roles. First, it serves as an electron-withdrawing substituent via its positive charge, and, second, together with its neighboring residue Glu 242 , it appears to be responsible for the lower symmetry of the heme group and distortion from the planar conformation normally seen in heme-containing proteins.In the family of mammalian peroxidases, myeloperoxidase (MPO) 1 is an extraordinary peroxidase. First of all, the enzyme is the only mammalian peroxidase known to peroxidize chloride to hypochlorous acid at a substantial rate. Secondly, MPO differs in its spectroscopic characteristics by its unusual redshifted Soret band in the optical absorbance as well in its pyridine hemochrome spectrum, its complicated resonance Raman spectrum, and its inverted sign pattern of the Soret band in the MCD spectrum (1-6). Those differences have been attributed to the special nature or structure of the heme group in MPO. Because this heme is covalently bound to the protein, characterization of this chromophore has been difficult. Based on different spectroscopic techniques, a formyl-containing heme a, a chlorin, and a heme b prosthetic group have been proposed in the past (3,5,(7)(8)(9).Although the enzyme differs in spectroscopic and catalytic properties, the homology between MPO and the other mammalian peroxidases is high. MPO shares respectively 70, 61, and 47% identical residues with eosinophil peroxidase (EPO), lactoperoxidase (LPO), and thyroid peroxidase (TPO) (10 -12), and an even higher homology can be found among the residues in the active site. MPO is the only mammalian peroxidase for which a crystal structure is known, at 2.3 Å resolution (13). The structural data for human MPO suggested that three heme substituents form covalent bonds with amino acid side chains in the protein. Two ester bonds were claimed to be present, between modified methyl groups on pyrrole rings A and C and the amino acids Glu 242 and Asp 94 . In a recent study, we have provided the first direct evidence by FTIR difference spectroscopy that ester bonds link the heme groups in all mammalian peroxidases via the conser...

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 95%

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The Sulfonium Ion Linkage in Myeloperoxidase

Kooter¹,

Moguilevsky²,

Bollen³

et al. 1999

Journal of Biological Chemistry

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“…Similarly, based on RR and EPR studies (25) as well as on its sensitivity to autocleavage of the Met 243 -Pro 244 peptide bond (10,24,25), it was proposed that E242Q has an intact Met 243 to heme linkage. Nevertheless, the impact of loss of the two individual ester bonds on ligand binding and redox reactivity is significantly different.…”

Section: Discussionmentioning

confidence: 99%

“…A third covalent link was identified as a sulfonium ion linkage between the sulfur atom of Met 243 and the terminal ␤-carbon of the vinyl group on pyrrole ring A ( Fig. 1) (8,10). In the homologous peroxidases (EPO, LPO, and TPO) the three-dimensional structure (LPO, Protein Data Bank code 2GJ1) and mass spectrometric analyses show that the heme is also covalently attached to the protein via two ester linkages.…”

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confidence: 99%