Primary structures of two low molecular weight proteinase inhibitors from potatoes

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Abstract
The amino acid sequences of 2 low MW proteinase inhibitors from Russet Burbank potatoes were determined. One of these, a chymotrypsin inhibitor, is a peptide of 52 amino acid residues, while the 2nd inhibitor, which is specific for trypsin, contains 51 amino acid residues. These peptides are highly homologous, differing at only 9 positions. At position 38, the chymotrypsin inhibitor possesses leucine and the trypsin inhibitor, an arginine. This difference probably represents the P1 sites, which are consistent with the respective specificities of the 2 inhibitors. The inhibitors are also homologous with potato inhibitor II and with an inhibitor previously isolated from eggplants.