Biphasic Time Course of Solubilization of Nitrogenase During Cavitation of Aerobically Grown Anabaena Cylindrica1

SUMMARY The nitrogenase activity of extracts from aerobically grown. Anabaena cylindrica is proportional to the cube of the concentration of extract over a wide range of activities. This relationship is changed to one of direct proportionality, approximately, when reaction mixtures are supplemented with a constant amount of extract from algae starved for molybdenum in the presence of tungstate. The time course of solubilization of nitrogenase during cavitation is reevaluated in the light of these results. The finding that solubilization occurs at first rapidly and subsequently much more slowly is discussed with reference to the hypothesis that nitrogenase is localized in heterocysts.