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Updated: Oct 15, 2025

Preparation of Rat Skeletal Muscle Homogenates for Nitrate and Nitrite Measurements
Published on: July 29, 2021
Influence of heme propionates on the nitrite reductase activity of myoglobin
Mary Grace I Galinato1, Aaron M Trail1, Olivia R Steinbeck1
1School of Science-Chemistry, Penn State Behrend, Erie, PA 16563, United States of America.
Abstract:
The heme propionates in myoglobin (Mb) form a H-bonding network among several residues within its second-sphere coordination, providing a key structural role towards Mb's functional properties. Our work aims to understand the role of the heme propionates on the nitrite reductase (NiR) activity (e.g. reduction of NO2- to NO) of this globin by studying an artificial dimethylester heme-substituted horse heart Mb (DME-Mb). The minor structural change brought about by esterification of the heme propionates causes the NiR rate to increase by more than over two-fold (5.6 ± 0.1 M-1 s-1) relative to wildtype (wt) Mb (2.3 ± 0.1 M-1 s-1). The lower pKa observed in DME-Mb may enhance the tendency of His64 towards protonation, therefore increasing the NiR rate. In addition, the nitrite binding constant (Knitrite) for DME-MbIII is greater than wt MbIII (350 M-1 versus 120 M-1). The disparity in the NiR activity correlates with the differences in electrostatic behavior, which influences the system's reactivity towards the approaching NO2- ion, and thus the formation of the FeII-NO2- intermediate.
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