Amino acid sequence of phospholipase A(2) from the pyloric ceca of starfish Asterina pectinifera

The complete amino acid sequence of phospholipase A(2) (PLA(2)) from the py loric ceca of the starfish Asterina pectinifera was determined by automated Edman degradation. The A. pectinifera PLA(2) (APLA(2)) consists of 137 ami no acids with an unblocked N-terminus and its molecular weight is calculate d to be 15 300.1. The enzyme contains 14 cysteine (Cys) residues at the cor responding positions of the same residues which have been shown to be invol ved in intramolecular disulfide bonds in mammalian pancreatic PLA(2). The r egion involving an active site and a Ca2+-binding loop shows fairly high se quence homology (75%) between the APLA(2) and porcine pancreatic PLA(2). Th e APLA(2) conserved the amino acid sequence of the loop portion of the porc ine pancreatic PLA(2) except for the deletion of two amino acids. These fea tures indicate that the APLA(2) can be classified into the group 1 type PLA (2). In contrast, the homology between the APLA(2) and porcine pancreatic P LA(2) was calculated to be 47% in the whole region. Further, the insertion of sixteen residues and the deletion of three residues were required in the sequence of the APLA(2) to align the corresponding region to the beta-wing of porcine pancreatic PLA(2). These differences in amino acid sequence of the APLA(2) may account for its specific properties such as the higher acti vity and the characteristic substrate specificity.