Nitric oxide oscillations in Paracoccus denitrificans: the effects of environmental factors and of segregating nitrite reductase and nitric oxide reductase into separate cells

Abstract

Nitric oxide is a denitrification intermediate which is produced from nitrite and then further converted via nitrous oxide to nitrogen. Here, the effect of low concentrations of the protonophore carbonylcyanide m-chlorophenylhydrazone on the time courses for dissolved gases was examined. While NO was found to oscillate, N 2O only increased gradually as the reduction of nitrite progressed. The frequency and shape of protonophore-induced NO oscillations were influenced by temperature and the concentration of electron donor N, N, N′, N′-tetramethyl- p-phenylene diamine (TMPD) in a manner compatible with the observed differential effects on the two involved enzyme activities. We demonstrated the existence of a pH interval, where [NO] oscillates even without uncoupler addition. Occurrence of nitric oxide oscillations in mixtures of a nitrite reductase mutant with a nitric oxide reductase mutant suggests that they cannot be due to a competition of the enzymes for redox equivalents from one common respiratory chain.