A complementary DNA sequence that predicts a human pancreatic amylase primary structure consistent with the electrophoretic mobility of the common isozyme, Amy2 A.

We report the nucleotide sequence of mRNA for the common electrophoretic isozyme of human pancreatic alpha-amylase, Amy2 A. The sequence was derived from a nearly full-length complementary DNA (cDNA) isolated from a cloned cDNA library. The relatively short 5' untranslated region (15 nucleotides) was determined by primer-extension sequencing. The human Amy2 messenger codes for a 511-residue preamylase polypeptide. An amino-terminal signal peptide of 15 amino acids with an Ala X Gln cleavage site is proposed based on homology to mouse, dog and hog amylases. The Amy2 A mRNA sequence differs from a recently reported human Amy2 sequence. Differences were found at 31 nucleotide positions. The alpha-amylase proteins predicted by the two mRNAs differ at 17 amino acid positions. Relative to the known sequences of other mammalian amylases, most of the differences between the two human Amy2 sequences appear to have occurred as substitutions in the sequence reported by Nakamura et al. (1984). These substitutions predict a protein with a substantially greater net negative charge than that of Amy2 A. We suggest that the two sequences may represent either divergent Amy2 alleles or the expression of non-allelic pancreatic amylase genes.