In this study, the treatment of $H_2O_2$, papain and acylation on the protein isolate obtained from defatted sesame oil cake for the changes in amino acids composition, color, digestibility and some functional characteristics of this protein were investigated. The results showed that $H_2O_2$, papain and papain $H_2O_2$ treatment increased the rates of the protein extraction and content of protein in protein isolates when those values were compared to the alkali treatment. Also amino acid composition of the protein isolates were comparatively good, and color, and functional properties and pepsin digestibility were markedly improved. The amount of lysine, the first limiting amino acid of this protein was increased. The solubility, bulk density, water absorption, fat absorption and emulsifying properties were remarkably improved while foaming properties and digestibility was slighly decreased.