Porcine pancreatic lipase. Sequence of the first 234 amino acids of the peptide chain

The single polypeptide chain of about 460 amino acids of porcine pancreatic lipase (EC 3.1.1.3) has been fragmented into five peptides by cyanogen bromide cleavage [Rovery, M., Bianchetta, J. & Guidoni, A. (1973) Biochim. Biophys. Acta, 328, 391--395]. The sequence of the first three cyanogen bromide peptides (CNI, CNII, CNIII), including a total of 234 amino acids, was fully elucidated. Automatic or manual Edman degradation was performed on the different peptides. Fragmentations of the CN peptides were accomplished by digestions with trypsin (after citraconylation or 1,2-cyclohexanedione treatment), chymotrypsin and Staphylococcus aureus external protease. Hydrolysis of unreduced material by pepsin and thermolysin, performed in order to determine the S-S bridge positions, provided useful overlapping peptides. The glycan moiety of lipase is bound to Asn-166. The non-essential tyrosine specifically blocked by diisopropylphosphorofluoridate is Tyr-49 in a cluster of asparagine and glutamine residues. The existence of a highly hydrophobic sequence (206--217) at the C terminus of the CNII fragment is noteworthy.