Open AccessAmino acid sequence and disulfide bridges of subunit III, a defective endopeptidase present in the bovine pancreatic 6 S procarboxypeptidase A complex
Author(s) -
VENOT Nicole,
SCIAKY Martine,
PUIGSERVER Antoine,
DESNUELLE Pierre,
LAURENT Georgette
Publication year - 1986
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1986.tb09642.x
Subject(s) - protein subunit , biochemistry , amino acid , carboxypeptidase , carboxypeptidase a , endopeptidase , peptide sequence , chymotrypsinogen , serine , pancreatic elastase , chemistry , trypsin , biology , enzyme , chymotrypsin , elastase , gene
The sequence of the 240 amino acids and the position of the five S‐S bridges of subunit III of the bovine pancreatic 6 S procarboxypeptidase A complex have been determined thus confirming its phylogenetic filiation with the pancreatic serine endopeptidase group. The subunit contains at equivalent positions all the elements of the catalytic site of these enzymes. The elements of a binding pocket very similar to that of porcine elastase I are also present in the protein thus accounting for its zymogen‐like activity. The most obvious difference is the absence in the subunit of the two strongly hydrophobic amino acids (16 and 17 in the chymotrypsinogen numbering), which are known to participate in the stabilization of a fully functional binding pocket in active endopeptidases. Four of the five disulfide bridges of subunit III are homologous with those common to all pancreatic endopeptidases. In contrast the fifth bridge forms a very small loop of only four amino acids, which is not encountered in active endopeptidases. Other potentially lethal modifications in the structure of the subunit are not excluded.