CELLULAR-LOCALIZATION OF THE INVERTASE, PROTEINACEOUS INHIBITOR AND LECTIN FROM POTATO-TUBERS

The activity of the acid beta-D-fructofuranoside fructohydrolase from Solanum tuberosum is thought to be modulated by a proteinaceous inhibitor. However, the invertase is also inhibited by the S. tuberosum agglutinin, and fructose is able to modulate the enzyme activity in vitro. These facts cast doubt on the physiological role of the proteinaceous inhibitor. The present paper shows that the soluble acid invertase from S. tuberosum and most of the cell sucrose occur in vacuoles together with fructose and glucose. The proteinaceous inhibitor and the lectin were found together in the partially digested cell wall. From these results an in vivo action of the proteinaceous inhibitor upon the soluble acid invertase is unlikely.