Partial amino acid sequences of α-amylase isozymes from barley malt

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Barley malt α-amylases 1 and 2, the low and high pI isozymes, respectively, were isolated and characterized by partial amino acid sequencing. The NH2-terminal sequence of α-amylase 1 and the sequence of a peptide fragment of this protein obtained by cleavage with hydroxylamine matched the primary structure previously deduced from the nucleotide sequence of a barley α-amylase cDNA clone. In distinction to α-amylase 1, the homologous protein α-amylase 2 had a blocked NH2-terminus, presumably a pyroglutamic acid residue. Sequenced peptide fragments from α-amylase 2 matched the amino acid sequence previously derived from a cDNA clone corresponding to a barley α-amylase different from α-amylase 1.