Processing of a 58 × 10³M_r Invertase From Potato-tubers

Processing of a 58 × 103Mr acid invertase to a 48 × 103Mr polypeptide has been demonstrated in potato tuber extracts using antibodies raised against a synthetic N-terminal peptide. Processing of the 58 × 103Mr protein occurred during the preparation of extracts in acetate buffer, pH 5.2, but not in Tris-HCI buffer, pH 7.5. A modified rapid extraction procedure suggested that the processing event also occurred in planta. Processing apparently increased the activity of acid invertase after foaming, a technique previously reported to dissociate the potato tuber invertase from an endogenous inhibitor. Western blot analysis revealed that the relative abundance of the 48 × 103Mr polypeptide was correlated with acid invertase activity.