Mechanism of substrate inhibition in cytochrome-c dependent NO reductases from denitrifying bacteria (cNORs).

ABSTRACT: Steady-state kinetics of cytochrome-c dependent denitrifying NO reductases (cNORs) show evidence of substrate inhibition at NO concentrations higher than 10 μM, but the mechanism of inhibition remains unclear. Here, we present low-temperature FTIR photolysis experiments carried out on the NO complex formed by addition of NO to the oxidized cNORs. A differential signal at 1261 cm^-1 that downshifts with ¹⁵NO and ¹⁵N¹⁸O is assigned to a ν(NO₂) from a bridging diiron-nitrito complex at the heme-nonheme diron site. Theoretical calculations reproduces observed frequencies and isotope shifts. Our experimental results confirm a prior theoretical study by Blomberg and Siegbahn [Blomberg, M. R., and Siegbahn, P. E. M. Biochemistry 2012, 51, 5173

SUBMITTER: Matsumura H 

PROVIDER: S-EPMC9007887 | biostudies-literature | 2022 Jun

REPOSITORIES: biostudies-literature