Synthesis and Degradation of Nitrite Reductase in Pea Leaves

We have shown in a previous publication (Gupta, Beevers 1983 J Exp Bot 34: 1455-1462) that the level of extractable nitrite reductase activity in pea (Pisum sativum cv Burpeeana) leaves is subject to environmental perturbations. In the current study, we have used rocket immunoelectrophoresis to quantitate the level of nitrite reductase protein in extracts from pea plants subjected to various environmental treatments. The level of nitrite reductase cross-reacting material closely followed the level of assayable nitrite reductase activity. The environmental conditions which enhanced the level of extractable nitrite reductase activity resulted in an increased level of nitrite reductase cross-reacting material in the extracts. In contrast, environmental conditions which resulted in a decrease in the level of extractable nitrite reductase activity produced a decline in cross-reacting material. These results indicate that the environmentally induced modulation of extractable nitrite reductase activity involves alteration of enzyme level and is not mediated by a reversible activation-inactivation of the existing enzyme.