The Alteration of Intracellular Enzymes Hi. Th~ Effect of Temperature on the Kinetics of Altered and Unaltered Yeast Catalase*

INTRODUCTION As a result of certain similarities in behavior between surface-unfolded (3) and intracellular erythrocyte catalase (4), the hypothesis was advanced "that catalase within the cell exists partially, but reversibly, unfolded at some intracellular interface; upon cytolysis, the enzyme is desorbed from the interface and changed to the roUed-up (native), soluble condition, with consequent increase in a c t i v i t y . . . " . The series of investigations of which this is part is designed to put this interracial hypothesis to the test. In the first of these papers ((1) hereafter referred to as Paper I), it was shown that the catalase of the intact yeast cell could be caused to undergo in situ an abrupt change in a wide variety of properties and thus made to imitate in almost every detail the behavior of catalase extracted from the cell into solution. The process by which this change was brought about was called enzyme alteration, and the existence of this phenomenon was taken to indicate that catalase could exist in no less than 2 distinct states, the rolled-up, highly active, soluble configuration (in which it is usually studied) which it possesses following alteration in situ or after extraction, and also the configuration, whatever it may be, which it possesses within the intact cell. Those properties of the intracellular catalase which underwent change were: (a) its specific activity,