The metabolic control of nitrite reductase in Neurospora crassa

A new assay system for nitrite reductase from Neurospora crassa is desribed in which sodium dithionite is used as the electron donor. The specific activity of nitrite reductase in crude extracts measured by this assay is higher than that reported by most previous workers.Nitrite reductase appears to be a derepressible, rather than an inducible enzyme because a high level of the enzyme is found in extracts of mycelia exposed to media containing no nitrogen source for 18 h, and because nitrate does not appear to relieve the partial repression of nitrite reductase caused by a Casamino-acid digest.