Amylase on Pecten maximus (Mollusca, bivalves): protein and cDNA characterization; quantification of the expression in the digestive gland.

The digestive enzyme alpha-amylase in Pecten maximus has been purified from the digestive gland, where it is present as two isoforms, In order to gain information on its structure and regulation, a digestive gland cDNA library, constructed in lambda phage Zap II (Stratagene, La Jolla, Calif., U.S.A.), was screened with a shrimp alpha-amylase cDNA probe. Only 0.02% of the clones were positive, and the longest clone, having a size of 1700 bp and identical to that of the mRNA, was fully sequenced. It contains the complete cDNA coding frame for one of the amylase isoforms of P. maximus. The deduced protein sequence is 508 amino acids long, with a putative 18 amino acid, highly hydrophobic signal peptide and a mature enzyme of 489 residues. The molecular weight corresponds to 54,500 Da and the calculated isoelectric point is 6.76. Locations of conserved sequences confirms the high level of similarity with the other members of the family.