Biochemical characterization of human S-nitrosohemoglobin. Effects on oxygen binding and transnitrosation

Academic Article

Abstract

  • S-Nitrosation of cysteine β93 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.
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    Digital Object Identifier (doi)

    Author List

  • Patel RP; Hogg N; Spencer NY; Kalyanaraman B; Matalon S; Darley-Usmar VM
  • Start Page

  • 15487
  • End Page

  • 15492
  • Volume

  • 274
  • Issue

  • 22