Comparison of the alpha-amylase inhibitor-1 from common beans and transgenic pea expressing the bean alpha-amylase inhibitor-1 by means of LC–TOF–MS

Abstract Recently, more attention is given to legume seed derived alpha amylase inhibitors (αAI) as it seems they effectively can be applied in crop protection against attack by insect larvae and prevention of obesity, weight control or diabetes type 2 diseases. Several researches have described the structure-function relationship of bean αAI-1. Some heterogeneous structural variations were revealed in their biologically active α− and β-chains due to the different amino acid composition and glycan patterns. However, further accumulation of the data is still required for the variability assessment of the bean αAIs and its transgenic expression. Five Phaseolus vulgaris bean varieties (Tendergreen, Huanita Dry, Bush, Red- Kidney and Pinto beans) derived αAI-1 and a genetically modified pea derived αAI-1 were investigated for comparison of their polypeptides, molecular weight, isoelectric points and their antigenicity. Differences were found in isoelectric points of the αAI-1's obtained from the P. vulgaris varieties and from the genetically modified pea using SDS-PAGE and two-dimensional gel electrophoresis (2-DE). Our data showed that the processed forms of αAI-1s were characterized as isoproteins at two isoelectric point values. Antibodies against Tendergreen bean αAI-1 developed in rabbit recognized all the investigated αAI-1s in immunoblotting. Mass-spectrometry was used to assess the presence of tryptic digested peptides including two peptide markers (AFYSAPIQIR for the α-chain, and SAVGLDFVLVPVQPESK for the β-chain) in the αAI-1s after 2-DE separation. Differences were observed in the presence of α-and β-chain peptides in the different αAI-1s.