PEPTIDE-MAPPING OF PEANUT PROTEINS - IDENTIFICATION OF PEPTIDES AS POTENTIAL INDICATORS OF PEANUT MATURITY

Proteins are the major source of peanut flavor precursors such as pept ides and amino acids. Changes in the protein structure possibly would lead to a change in peanut flavor quality. As peanut maturity can affe ct peanut flavor quality, it was postulated that proteins between matu re and immature peanuts could be structurally different. To support th is postulation, peptide mapping of mature and immature peanut proteins was carried out. Peptide maps were produced by digesting peanut prote ins with an arginyl endopeptidase. This was followed by treatment of t he resultant protein digests with trichloroacetic acid (TCA) or an aff inity column of immobilized anhydrotrypsin (IMAT). The TCA-soluble pep tide fractions were then subjected to analyses by C18 reversed-phase h igh-performance liquid chromatography (HPLC), whereas fractions, which contained carboxyl- or C-terminal and non-C-terminal peptides, from t he IMAT column were analyzed by capillary zone electrophoresis (CZE). For resolution purposes, fractions collected from the C18 column of HP LC were further analyzed by CZE. Results showed that peptide maps from immature peanut proteins contained peptides different from those from mature peanut proteins. Peptides such as peptide I (a C-terminal pept ide) from immature peanut proteins and peptide M (a TCA-soluble peptid e) from mature peanut proteins were identified. This difference in pep tide patterns indicates that proteins between mature and immature pean uts were structurally different.