Subunit structure and functional properties of the predominant globulin of perilla (Perilla frutescens var. frutescens) seeds

Abstract

Approximately 40% of defatted perilla seeds consists of proteins which are primarily composed of globulin (84%). The amino acid profile of perilla proteins demonstrated balanced amounts of all essential amino acids, except for lysine. The molecular mass of the predominant globulin was estimated to be 340 kDa by gel filtration. This globulin was separated into three intermediary subunits (54, 57 and 59 kDa) by SDS-PAGE. It is suggested from these results that the globulin exists as a hexamer. A treatment with 50 mM dithiothreitol enabled the intermediary subunits to be separated into three acidic subunits (31-34 kDa) and four basic subunits (23-25 kDa). It is interesting that this subunit structure is the same as that of sesame α-globulin, despite them coming from different families. Compared to sesame α-globulin, the heat-induced gel of perilla globulin had better water-holding ability, despite it displaying the same degree of gel hardness.