The importance of disulfide bridges in human endopeptidase (enkephalinase) after proteolytic cleavage.
The neutral endopeptidase (NEP) is a membrane-bound enzyme, which is solubilized by treatment with the protease, papain. Papain did not affect the apparent catalytic activity or the molecular mass of the purified human enzyme in SDS-PAGE. When NEP was treated with a reducing agent after papain digestion, it dissociated into smaller, lower molecular mass fragments. Amino acid analysis and s-carboxymethylation of the half cystine residues indicated that NEP contains four S-S bridges. We concluded that, although covalent bonds appear to be cleaved in NEP by papain, its activity and structure are sustained by S-S bridges.
D000596:Amino Acids / Q000032:analysis; D002384:Catalysis; D055598:Chemical Phenomena; D002621:Chemistry; D004220:Disulfides / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases; D006801:Humans; D007668:Kidney / Q000201:enzymology; D015260:Neprilysin; D010206:Papain; D013329:Structure-Activity Relationship
D000596:Amino Acids; D004220:Disulfides; D010450:Endopeptidases; D010206:Papain; D015260:Neprilysin