Similarity of the Kinetics of Invertase Action in Vivo and in Vitro. Ii

1. The pH-activity relationship of invertase has been studied in vivo and in vitro under identical external environmental conditions. 2. The effect of changing (H(+)) upon the sucroclastic activity of living cells of S. cerevisiae and of invertase solutions obtained therefrom has been found, within experimental error, to be identical. 3. The region of living yeast cells in which invertase exerts its physiological activity changes its pH freely and to the same extent as that of the suspending medium. It is suggested that this may indicate that this intracellular enzyme may perform its work somewhere in the outer region of the cell. 4. In using live cells containing maltase, no evidence of increased sucroclastic activity around pH 6.9, due to the action of Weidenhagen's alpha-glucosidase (maltase), was found.