title: Structure of the novel heme adduct formed during the reaction of human hemoglobin with BrCCl3 in red cell lysates.
abstract: It was previously shown that the reductive debromination of BrCCl3 to trichloromethyl radical by human hemoglobin leads to formation of dissociable altered heme products, two of which are identical to those formed from myoglobin and one which is novel. In this study, we have elucidated the structure of this novel adduct with the use of mass spectrometry, as well as 1H and 13C NMR as a substitution product of a -C(Cl) = CCl2 moiety for a beta-hydrogen atom on the prosthetic heme's ring I vinyl group. From studies with the use of 13C-enriched BrCCl3, it was determined that the added carbon atoms were derived from 2 eq of BrCCl3. A mechanism that involves multiple reductive events and a radical cation heme intermediate is proposed. Consistent with this mechanism, cellular reductants were found to selectively enhance the amount of this novel dissociable heme adduct. These studies reveal fine differences between myoglobin and hemoglobin in the accessibility of reactive intermediates to the ring I vinyl group, as well as the potential importance of cellular reductants on the course of heme alteration.
authors.affiliation: Laboratories of Chemical Pharmacology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Y
authors.initials: Y
authors.lastname: Osawa
authors.forename: C S
authors.initials: CS
authors.lastname: Fellows
authors.forename: C A
authors.initials: CA
authors.lastname: Meyer
authors.forename: A
authors.initials: A
authors.lastname: Woods
authors.forename: J A
authors.initials: JA
authors.lastname: Castoro
authors.forename: R J
authors.initials: RJ
authors.lastname: Cotter
authors.forename: C L
authors.initials: CL
authors.lastname: Wilkins
authors.forename: R J
authors.initials: RJ
authors.lastname: Highet
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology; D001665:Binding Sites; D001975:Bromotrichloromethane / Q000097:blood* / Q000378:metabolism; D002247:Carbon Isotopes; D004912:Erythrocytes / Q000378:metabolism*; D005978:Glutathione / Q000494:pharmacology; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006454:Hemoglobins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D006461:Hemolysis; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009211:Myoglobin / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D006454:Hemoglobins; D009211:Myoglobin; D006418:Heme; D005978:Glutathione; D001975:Bromotrichloromethane; D001205:Ascorbic Acid