Guenter Schwarz - C 13

Sulfite oxidase-dependent nitric oxide synthesis: Molecular mechanism, in vivo relevance and pharmacological targeting


Nitric oxide (NO) is an important signaling molecule in a large variety of physiological and pathological processes. Besides the important and various functions of the classical three NO synthases there is growing evidence that nitrite plays a critical role in controlling NO homeostasis and mediated long-lasting effects in a variety of processes such as blood pressure, hypoxic vasodilation, and cellular cytoprotection.
     During the previous funding period we established mitochondrial sulfite oxidase (SOX) as novel nitrite reductase in vitro and in cellulo (Wang et al. ARS 2015). We demonstrated that nitrite-dependent NO synthesis requires the molybdenum domain of SOX and identified MoIV as reactive species of the enzyme. By direct NO detection we determined kinetic parameters for NO synthesis and were able to run the enzyme with all three substrates (sulfite, nitrite, cytochrome cox) in a catalytic manner producing sulfate, cytochrome cred and NO in a 1:1:1 ratio. Our mechanistic studies further disclosed an inverse relationship between the rate of electron transfer from MoIV to the heme iron and the rate of NO synthesis.
    This project aims to demonstrate the importance of SOX-dependent NO synthesis in vivo. We propose that SOX-dependent NO synthesis provides a missing link in the regulation of mitochondrial respiration by nitrite and NO. Animal models with altered NO activity will be used to demonstrate SOX-dependent control of blood pressure by nitrite reduction. Finally, we aim to screen for substances that increase NO synthesis.

Clinical/medical relevance and sustainability in disease understanding

Ischemia/reperfusion injury underlies the progression of pathologies in various organs and is a significant cause of morbidity and mortality. Management of cardiovascular disorders critically dependents on blood pressure control by NO. With SOX, as novel NO-synthase, we found an entirely new target for pharmacological targeting of nitrite-dependent NO release. Given our previous experience in drug development, we aim to find now compounds for the treatment of hypertension disorders.

Prof. Dr. rer. nat. Guenter Schwarz

Institute for Biochemistry

Prof. Dr. rer. nat. Guenter Schwarz

Vice Chair / Dean - Faculty of Mathematics and Natural Sciences
Principal Investigator C 13

Work +49 221 470 6441

Fax (Work) +49 221 470 5092

Institute for Biochemistry
Zülpicher Str. 47
50674 Cologne

Publications - Guenter Schwarz

Link to PubMed