Cardiac myoglobin participates in the metabolic pathway of selenium in
rats
ABSTRACT
As an essential micronutrient, selenium deficiency is a leading cause of
cardiovascular diseases. The heart is continuously beating to deliver blood
to the entire body, and this requires a high amount of energy. An adult
heart normally obtains 50–70% of its adenosine 50-triphosphate from fatty
acid b-oxidation. An increase in fatty acid oxidation activity induces
the generation of larger amounts of by-products (reactive oxygen species,
ROS) from mitochondrial oxidative phosphorylation. Seleniumdependent glutathione
peroxidases play a critical role in the removal of these ROS, especially
organic hydroperoxides, from the heart. The definitive transport and/or
detailed metabolic pathways from the selenium-source compounds to the selenoproteins
in the heart still remain unclear. We explored the selenium-binding proteins
in a rat cardiac cell lysate using its reactive metabolic intermediate,
selenotrisulfide (STS), and MALDI TOF-mass spectrometry. Several proteins
with a free cysteine (Cys) thiol were found to be reactive with STS through
a thiol-exchange reaction. The most distinctive Cys-containing protein
in the cardiac cell lysate was identified as myoglobin (Mb) from a rat
protein database search and tryptic fragmentation experiments. When separately
examined in selenium adequate rats, selenium-binding to the cardiac Mb
was verified using selenium-specific fluorometry. Cardiac Mb is thought
to participate in the selenium metabolic pathway in the heart.