Molecular organization of human L' and L pyruvate kinases.
Extremities, peptide maps and phosphorylatable site localization of human erythrocyte L' and liver L pyruvate kinases (EC 2.7.1.40) were investigated. L' and L subunits seemed to have similar, blocked NH2 termini and differ in their sensitivity to carboxypeptidase A, that is to say in their C-terminal ends. After digestion by Staphylococcus aureus V8 protease, the phosphorylated sites of both L' and L subunits were located on those peptides which were different in L' and L, that is to say on the C-terminal sides. A mild proteolytic attack of the native tetrameric enzymes by trypsin partially degraded the phosphorylatable peptides without removing the phosphoserine residue; in the same conditions, chymotrypsin split off this phosphorylated residue and subtilisin totally degraded the phosphorylated peptides. From these results it appears, therefore, that age-dependent proteolytic degradation of L' subunits in old red cells involves the C-terminal side of the molecules, ultimately resulting in cleavage of the phosphorylated site. Since erythrocyte L' and liver L subunits are encoded by different species of messenger RNAs, our results indicate, in addition, that these messenger RNA species should differ by their 3' coding sequences.
D002268:Carboxypeptidases; D043422:Carboxypeptidases A; D010450:Endopeptidases; D004912:Erythrocytes / Q000201:enzymology; D006801:Humans; D046911:Macromolecular Substances; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D011487:Protein Conformation; D011770:Pyruvate Kinase / Q000097:blood* / Q000302:isolation & purification; D012697:Serine Endopeptidases
D046911:Macromolecular Substances; D010446:Peptide Fragments; D011770:Pyruvate Kinase; D002268:Carboxypeptidases; D010450:Endopeptidases; D043422:Carboxypeptidases A; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase