Binding of pyruvate oxidase alpha-peptide to phospholipid vesicles

The alpha-peptide of pyruvate oxidase is a 23 residue peptide which is cleaved from the carboxy terminus of the enzyme during proteolytic activation by chymotrypsin (M. Recny et al. (1985) J. Biol. Chem. 260, 14287-14291). Cleavage of alpha-peptide results in the loss of the high affinity lipid-binding site in the enzyme. The beta-peptide of pyruvate oxidase is a 101 residue peptide which also is cleaved from the carboxy terminus of pyruvate oxidase. Cleavage of the beta-peptide from pyruvate oxidase results in the inactivation of the enzyme. The beta-peptide includes the alpha-peptide amino acid sequences at its carboxyl terminus. We now report on the binding of the alpha- and beta-peptides to phospholipid vesicles. Both peptides bind with equal and high affinity to phosphatidylcholine vesicles. We conclude from these results that the alpha-peptide furnishes the membrane-binding site which plays the physiologically important role in the activation of this peripheral membrane enzyme.