The purification, N-terminal amino acid sequence and some other properties of an αM-subunit of legumin from the pea (Pisum sativum L.)

An α^M-subunit of legumin from Pisum sativum has been purified from a genotype which showed no α^M-subunit heterogeneity on two-dimensional isofocusing/electrophoresis gels. N-terminal sequence analysis of the subunit showed it to be homologous to the acidic subunits of glycinin, from Glycine max, and particularly similar to glycinin subunit A₂. Amino acid analysis showed the α^M-subunit to contain three cysteine and three methionine residues per subunit, plus 14 lysine and 39 arginine. Fewer than the expected number of tryptic peptides from the α^M-subunit were resolved by two-dimensional peptide mapping, but the expected number could be detected by peptide mapping of α^M-subunits which had been hydrolysed with the arginine-specific protease from mouse submaxillary gland.