Publisher Summary Hemoglobin readily undergoes one-electron oxidations and reductions, and it can act as a source or sink of free radicals An autoxidation of the heme groups produces O2– and, indirectly, H2O2 Hemoglobin also interacts with redox-active xenobiotics and metabolites, forming the xenobiotic radical and initiating a series of reactions that generate other radicals and oxidant species and often result in oxidative denaturation of the hemoglobin This chapter focuses on the measurement of oxidant-mediated changes to hemoglobin It defines the different oxidation products of hemoglobin and briefly describes general mechanisms for their production The oxidation of oxyhemoglobin (oxyHb)4 gives O2– and methemoglobin (metHb) If the globin structure is destabilized, metHb can convert to hemichrome in which either the distal histidine or an external ligand occupies the sixth coordination position of the ferric heme Hemichromes precipitate readily and are the main constituent of Heinz bodies Choleglobin is a term used to describe denatured hemoglobin in which the porphyrin ring has been hydroxylated or broken open Ferrylhemoglobin (ferrylHb or Hb2+H2O2) is an Fe(IV) complex formed from ferrous hemoglobin and H2O2 The reaction of metHb with H2O2 produces short-lived ferryl radicals, which are Fe (IV) species with the additional oxidizing equivalent localized on the globin

Oxidative reactions of hemoglobin.

Specific covalent modification of thiols: Applications in the study of enzymes and other biomolecules

The nature of the association between the murine leukemia virus envelope proteins.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2893%2980051-U

Sulfhydryl oxidation induces rapid and reversible closure of the ATP-regulated K+ channel in the pancreatic β-cell

A Mn(2+)-dependent enzymic breakdown of allantoate has been detected in crude and partially purified extracts of developing soybeans. The products detected were CO(2), NH(3), glyoxylate, labile glyoxylate derivatives, and low levels of urea. Urea is initially produced at less than 10% the rate of urease-independent CO(2) release indicating that the activity is not allantoate amidinohydrolase (i.e. urea is not directly cleaved off allantoate). The urease-independent CO(2) releasing activity has an apparent K(m) of 1.0 millimolar for allantoate. Ethylenediaminetetraacetate, borate, and acetohydroxamate (all at 10 millimolar) inhibit the enzymic production of NH(3), CO(2), and labile glyoxylate derivatives from allantoate. However, the potent urease inhibitor, phenyl phosphordiamidate does not inhibit CO(2) and NH(3) release indicating that the action of acetohydroxamate is not due to its inhibition of urease. That the allantoatedegrading activity was more than 5-fold greater in seed coats than in embryos is consistent with the data of Rainbird et al. (Plant Physiol 1984 74: 329-334) which indicate that available ureides are metabolized before reaching the embryo. 2-Ethanolthio, 2'ureido, acetic acid (NH(2)COHNCHCO(2)HSCH(2)CH(2)OH), the first allantoate-derived product detected by HPLC analysis, is an addition produced of mercaptoethanol with an unidentified enzymically produced ureido intermediate that is not derived from ureidoglycolate or oxalurate.

D.R. Grassetti

Papers

The use of 2,2'-dithiobis-(5-nitropyridine) as a selective reagent for the detection of thiols.