HYDROXYLAMINE METABOLISM IN MONORAPHIDIUM BRAUNII

S ummary The utilization of nitrate by cells of Monoraphidium braunii Legnerová was immediately impaired by low concentrations of hydroxylamine. The consumption of NO 3 − resumed when almost no hydroxylamine was left in the culture medium but resumption took place only under illumination with blue light. The addition of hydroxylamine to cell suspensions caused the rapid inactivation of nitrate reductase. The inactivation was largely prevented by the previous incubation of the cells with menadione, a rinding which suggests that hydroxylamine inactivates the reduced form of nitrate reductase. Illumination of cells previously treated with hydroxylamine promoted the in situ reactivation of the enzyme.