Reactions between nitrosopersulfide and heme proteins

Area of Science:

• Biochemistry
• Chemical Biology
• Physiology

Background:

• Nitrosothiols react with hydrogen sulfide (H2S) to form nitrosopersulfide (SSNO-).
• The stability and biological role of SSNO- remain debated.
• Iron-containing proteins are abundant in the human body, necessitating study of their interactions with SSNO-.

Purpose of the Study:

• To investigate the stability of SSNO- in isolation.
• To determine the reactivity of SSNO- with various heme proteins.
• To elucidate the role of heme iron's oxidation state and heme accessibility in SSNO- reactions.

Main Methods:

• Time-resolved electron paramagnetic resonance (EPR) spectroscopy.
• UV-Vis absorption spectroscopy.
• Kinetic analysis of SSNO- reactions with hemoglobin variants.

Main Results:

• SSNO- was found to be relatively stable in isolation.
• Reaction of SSNO- with deoxyhemoglobin and deoxygenated methemoglobin produced iron-nitrosyl hemoglobin, indicating nitric oxide (NO) release.
• Substantial NO release and nitrosyl hemoglobin formation required a vacant heme site, with ferric iron in methemoglobin potentiating SSNO- reactivity.

Conclusions:

• SSNO- can serve as a source of NO.
• The reactivity of SSNO- with heme proteins is dependent on heme accessibility and iron oxidation state.
• Findings provide insights into the in vivo stability and reactivity of SSNO-, impacting NO and sulfide bioavailability.