Thionins

The general designation of thionins has been proposed for a family of homologous peptides that includes purothionins, which were first isolated from wheat seeds (Balls el #/., 1942) and their homologues from various taxa that have been named viscotoxins and crambins (see Garcia-Olmedo el al., 1989). The crystalline protein material obtained from lipid extracts of wheat endosperm was designated "purothionins" because of its high sulphur content (Balls el al., 1942). This material was found to have bactericidal and fungicidal properties (Stuart and Harris, 1942), to inhibit fermentation of wheat mashes (Balls and Harris, 1944), and to be toxic to laboratory animals (Coulson el al„ 1942). The toxic properties of mistletoes were ascribed to the viscumin lectin and to a mixture of small basic proteins, designated - "viscotoxins" (Samuelsson, 1974). In a study of the seeds of the Abyssinian cabbage {Crambe abyssinica)^ a high-sulphur crystalline protein was obtained from the aqueous acetone extracts and designated "crambin" (Van Ettcn e/<?/., 1965)