Purification and characterization of a new 11S globulin-like protein from Chinese jujube (Ziziphus jujube Mill.) seeds

Abstract

Around 8 million tons of jujube pomace containing seeds was produced each year in China; so how to utilize these residual matters has been receiving great attentions. The 11S globulins are the major storage proteins, and it can be used as additive agents in many food products with gelling and caking functionality. In the present study, an 11S globulin-like protein (ZSG) was isolated and purified from Chinese jujube (Ziziphus jujube Mill.) seeds by two consecutive anion exchange and size exclusion chromatography. A yield of 8 mg of the ZSG from 1 kg seeds was obtained. The apparent molecular mass of the native ZSG was found to be about 210 kDa. The protein consisted of two subunits with molecular masses of 26.0 kDa and 26.5 kDa, respectively. Amino acid composition analyses indicated that ZSG contained all eight essential amino acids, while lysine was the first limiting amino acids. N-terminal amino acid sequences of 26.0- and 26.5-kDa subunits are GVEETICTLRLLENI and GLEETVCSLRLKENI. The two peptide fragments of 26.0-kDa subunit are ANPDQVLENAFQISR and GVEETICTLR by LC–MS/MS. To the best of our knowledge, this is the first report on the purification of 11S globulin-like protein from Chinese jujube (Ziziphus jujube Mill.) seeds.