Structure of a major pea seed albumin: Implication of a free sulphydryl group

Recent studies in a number of laboratories have characterised many of the properties of a major pea albumin (designated PMA or PA2: subunit M r ∼26 000) which is not readily degraded in the cotyledon upon germination. In the present report, some of the physicochemical properties of this protein have been studied in greater detail. A non‐helical structure, stable at high pH, is evident. Of special significance is the presence of a single free sulphydryl group, although studies reported elsewhere show that the protein consists of four copies of a strongly conserved repeated sequence. It is postulated that this free sulphydryl group in PA2 (5–10% of total pea seed protein) causes polymerisation through disulphide interchange and thereby is a likely source of partial insolubility in protein isolates following an initial alkaline extraction.