Mass spectrometric analysis of plant protein concentrates

Abstract

The work is devoted to the study of the composition of protein concentrates from amaranth grains (Amaranthus hypochondriacus L.), Voronezh variety. Amaranth protein concentrates were obtained by the alkaline extraction of proteins, the neutralization of the solution, followed by ultrafiltration; by separating the starch fraction with amylolytic enzymes; alkaline extraction of proteins and their precipitation at pH 4.5. The conditions for protein extraction were selected, followed by gas chromatography-mass spectrometric analysis and their identification. It has been shown that proteins from amaranth grain were more efficiently extracted with a buffer containing urea at protein concentrations in solution of 1.7, 1.9, and 2.9 mg/cm3respectively, while the buffer with detergents was more effective for the extraction of low molecular weight proteins at protein concentrations in solution of 4.9, 2.9, and 9.0 mg/cm3 respectively. As a result of HPLC-MS/MS analysis followed by a search and identification in the UNIPROT database, it was established that the main protein of amaranth grain is 11S-globulin, which is a reserve protein of amaranth seeds. In amaranth concentrates, 14 unique proteins characteristic only for A.hipochondriacus L., as well as proteins that were not characteristic to this species, but were reliably identified. Based on the results of semi-quantitative analysis of the peptide profile of amaranth grain protein concentrates, a high frequency of occurrence of the main 11S-globulin proteins was established in all samples. The frequency of occurrence of other proteins in samples obtained by different methods differed significantly, which was associated with the peculiarities of protein isolation from amaranth grain. The obtained results can be used for the production of plant protein concentrates with a set protein composition.