Sesame water-soluble proteins fraction contains endopeptidases and exopeptidases with high activity: A natural source for plant proteases

Abstract

Recently, the interest in the plant proteases has greatly increased. However, only a few of proteases are isolated from the hugely produced oilseeds for the practical utilizations. In this study, the raw sesame milk prepared from peeled sesame seeds was separated into floating, skim, and precipitate fractions by centrifugation. The predominant aspartic endopeptidases and serine carboxypeptidases, which exerted high synergetic activity at pH 4.5–5 and 50–60 °C, were identified in the skim by the liquid chromatography tandem mass spectrometry, Tricine–sodium dodecyl sulfate–polyacrylamide gel electrophoresis, protease inhibitor assay, trichloroacetic acid–nitrogen soluble index (TCA–NSI), and free amino acid analyses. By incubating the mixture (protein content, 2%) of skim and precipitate at pH 4.5 and 50 °C for 6 h, the TCA–NSI and free amino acids achieved to 38.42% and 3148 mg/L, respectively. Moreover, these proteases efficiently degraded the proteins from soybean, peanut, and bovine milk.