Some effects of nitrogen-starvation on nitrogen and carbohydrate metabolism inAnkistrodesmus braunii

Enzymic activities have been measured in cell-free extracts from nitrogen-starved cultures ofAnkistrodesmus braunii. During ten hours of nitrogenstarvation the activities of the enzymes nitrite reductase (E.C.1.6.6.4), glutamic dehydrogenase (E.C.1.4.1.4), glutamine synthetase (E.C.6.3.1.2) and urea amidolyase (E.C.3.5.1.5) were derepressed while the activities of the enzymes malate dehydrogenase (E.C.1.1.1.37) and hexokinase (E.C.2.7.1.1) remained more or less unchanged. In contrast, the photosynthetic capacity of the nitrogen-starved cultures declined rapidly and accompanying this decline were losses in the activities of ribulose diphosphate carboxylase (E.C.4.1.1.39) and triose phosphate-NADP-dehydrogenase (E.C.1.2.1.13).