INVITRO DEGRADATION OF GASTRIC MUCIN - CARBOHYDRATE SIDE-CHAINS PROTECT POLYPEPTIDE CORE FROM PANCREATIC PROTEASES

  • 1 January 1983
    • journal article
    • research article
    • Vol. 84  (3) , 533-537
Abstract
The polypeptide core of mucin glycoprotein subunits resists cleavage by proteases. To determine if the carbohydrate side chains of these subunits protect the underlying polypeptide core from proteolytic cleavage, the effect of pancreatic proteases on hog gastric mucin before and after cleavage of its carbohydrate moieties by bacterial glycosidases from an anaerobic human fecal culture supernate was compared. Hog gastric mucin was resistant to pancreatic proteases: < 10% of the mucin protein became soluble in 80% vol/vol ethanol after 24-h incubation with trypsin, .alpha.-chymotrypsin and elastase, and its elution pattern from Sephadex G-200 remained unchanged after elastase treatment, with 90% eluting at the void volume. By contrast, after removal of 50% of its carbohydrates, mucin was susceptible to pancreatic proteases: 50% of mucin protein became soluble in 80% vol/vol ethanol after 24-h incubation with .alpha.-chymotrypsin and elastase, and 24% of mucin protein became soluble in 80% vol/vol ethanol after 24-h incubation with trypsin; after elastase treatment, its elution from Sephadex G-200 was markedly retarded. The carbohydrate side chains of hog gastric mucin glycoprotein apparently protects the underlying polypeptide core from proteolysis and degradation of the carbohydrate side chains by glycosidases from fecal bacteria may render the polypeptide core susceptible to pancreatic proteases.