A new route to carbon monoxide adducts of heme proteins

Abstract

Sulfoxylate SO 2 H −( SO 22−), a strong reducing agent readily produced by hydrolysis of thiourea dioxide, reacts with ferric myoglobin ( Mb ) to reversibly produce Fe (II)- Mb , starting from either aerobic or anaerobic conditions. Exposure of Fe (II)- Mb to excess sulfoxylate further produces Fe (II)- CO - Mb . Fe (II)- Mb can be regenerated by reoxidation with ferricyanide at this stage; hemin, rubredoxin and cytochrome c show a similar reactivity towards sulfoxylate. The source of CO is not the protein moiety, nor is it the heme or the thiourea dioxide – but rather CO 2, via its reaction with sulfoxylate when the latter is used in large excess. These findings provide a convenient single-step route to carbon monoxide heme adducts, without the need to manipulate toxic CO gas.