Electrophoretic analysis, redox activity, and other characteristics of proteins similar to purothionins from tomato (Lycopersicum esculentum), mango (Mangifera indica), papaya (Carica papaya), and walnut (Juglans nigra).
Daley L. S., Theriot L. J.
Author Affiliation: Dep. Hort., National Clonal Germplasm Repository, Oregon State Univ., Corvallis, OR 97331, USA.
Journal of Agricultural and Food Chemistry 35 : 680-687
Abstract : Low MW proteins stable to heat, acid, and organic solvents were extracted from tomato leaves and from mango, pawpaw and walnut seeds. These proteins were further purified by a new method utilizing triacylglycerol lipase (EC 3.1.1.3) and (diethylamino)ethyl-Sephadex. Electrophoretic analysis and assays for redox activity and interaction with crude non-reduced papain (EC 3.4.22.2 and EC 3.4.22.3) and the specific sulphydryl reagent ammonium 4-chloro-7-sulphobenzofuranozan showed that these proteins have the following characteristics:low MW, net positive charges, and electrophoretic migration characteristics similar to those of thionin; abundant sulphydryl groups; redox properties; and interactions with crude papain proteolytic activity. The possibility that these proteins may be thionins is discussed, and the pseudo-first-order kinetics of their reaction with insulin is demonstrated.