Some 2S albumin from peanut seeds exhibits inhibitory activity against Aspergillus flavus

A crude 2S albumin fraction was separated from peanut (Arachis hypogaea L.) cotyledons. Untreated 2S albumin had little inhibitory activity against trypsin, spore germination, or hyphal growth of Aspergillus flavus. However, following treatment of 2S albumin with SDS, increased inhibitory activity was demonstrated. We further purified 2S albumin using Sephadex G-100 and DEAE cellulose (DE-32) chromatography. HPLC analysis showed that the partially pure 2S albumin consisted of two polypeptides, whereas SDS-PAGE analyzes exhibited six polypeptides. One of the polypeptides, 2S-1, was found to contain the same molecular weight and enzymatic properties as the peanut protease inhibitor (PI); however, the N-terminal amino acid sequence of 2S-1 differed from that of PI. An NCBI database search revealed that the 2S-1 polypeptide is homologous to the pathogenesis-related proteins from soybean, cowpea, chickpea, and Lupinus luteus. We hypothesize that the 2S-1 polypeptide might represent a novel antifungal protein.