title: Biochemical characterization of human S-nitrosohemoglobin. Effects on oxygen binding and transnitrosation.
abstract: S-Nitrosation of cysteine beta93 in hemoglobin (S-nitrosohemoglobin (SNO-Hb)) occurs in vivo, and transnitrosation reactions of deoxygenated SNO-Hb are proposed as a mechanism leading to release of NO and control of blood flow. However, little is known of the oxygen binding properties of SNO-Hb or the effects of oxygen on transnitrosation between SNO-Hb and the dominant low molecular weight thiol in the red blood cell, GSH. These data are important as they would provide a biochemical framework to assess the physiological function of SNO-Hb. Our results demonstrate that SNO-Hb has a higher affinity for oxygen than native Hb. This implies that NO transfer from SNO-Hb in vivo would be limited to regions of extremely low oxygen tension if this were to occur from deoxygenated SNO-Hb. Furthermore, the kinetics of the transnitrosation reactions between GSH and SNO-Hb are relatively slow, making transfer of NO+ from SNO-Hb to GSH less likely as a mechanism to elicit vessel relaxation under conditions of low oxygen tension and over the circulatory lifetime of a given red blood cell. These data suggest that the reported oxygen-dependent promotion of S-nitrosation from SNO-Hb involves biochemical mechanisms that are not intrinsic to the Hb molecule.
authors.affiliation: Department of Pathology, Molecular and Cellular Division, University of Alabama at Birmingham, Birmingham, Alabama 35294-0019, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Patel
authors.forename: N
authors.initials: N
authors.lastname: Hogg
authors.forename: N Y
authors.initials: NY
authors.lastname: Spencer
authors.forename: B
authors.initials: B
authors.lastname: Kalyanaraman
authors.forename: S
authors.initials: S
authors.lastname: Matalon
authors.forename: V M
authors.initials: VM
authors.lastname: Darley-Usmar
mesh_terms: D000494:Allosteric Regulation; D003545:Cysteine / Q000031:analogs & derivatives* / Q000737:chemistry; D004912:Erythrocytes / Q000378:metabolism; D005033:Ethylmaleimide / Q000737:chemistry; D005978:Glutathione / Q000031:analogs & derivatives / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D015538:Nitrosation; D009603:Nitroso Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D010396:Penicillamine / Q000031:analogs & derivatives / Q000737:chemistry; D026422:S-Nitrosoglutathione; D026403:S-Nitrosothiols; D013053:Spectrophotometry; D013438:Sulfhydryl Compounds / Q000032:analysis; D014664:Vasodilation / Q000187:drug effects
chemical_list: D006454:Hemoglobins; D009603:Nitroso Compounds; D026403:S-Nitrosothiols; C110881:S-nitro-N-acetylpenicillamine; C103574:S-nitrosohemoglobin; D013438:Sulfhydryl Compounds; D026422:S-Nitrosoglutathione; C100003:deoxyhemoglobin; C021315:S-nitrosocysteine; D005978:Glutathione; D010396:Penicillamine; D003545:Cysteine; D005033:Ethylmaleimide; D010100:Oxygen