Source of Endoproteolytic Activity Associated with Purified Ribulose Bisphosphate Carboxylase

Abstract
The association of endoproteolytic activity with purified ribulose bisphosphate carboxylase (RuBPCase) from barley (Hordeum vulgare cv. Numar) leaves was investigated. RuBPCase purified by chromatography on agarose gel and diethylaminoethyl-cellulose was free of associated endoproteolytic activity. The addition of leupeptin and casein to the extraction buffer completely eliminated proteolysis during initial extraction of RuBPCase. Endoproteolytic activity previously found associated with RuBPCase was identified as being due to contamination of endoproteinases from broken vacuoles.