An insulin-binding protein was isolated from Canavalia ensiformis seed coat, by using an insulin-Sepharose 4B affinity chromatography, and the protein was identified as canavalin (Canavalia 7S globulin) by mass spectrometry analysis. The major novelty of these data is the acidic nature of this globulin insulin-binding, in contrast to the basic Bg-like insulin-binding proteins so far reported in plants.