The effects of ethionine administration and choline deficiency on protein carboxymethylase activity in mouse pancreas

Protein carboxymethylase of mouse pancreas is both soluble (70%) and particulate (30%). The Km for S-adenosylmethionine is 7.5 x 10(-7) M and the Ki for S-adenosylethionine is 1.3 . 10(-5) M. Administration of an ethionine containing diet results in a decrease in protein carboxymethylase activity. Ethionine ingestion also increases pancreatic amylase content by interfering with digestive enzyme discharge. The reciprocal changes in amylase content and protein carboxymethylase activity can be detected within 12 h of commencing the ethionine administration and are enhanced by simultaneous choline deficiency. These studies support the hypothesis that protein carboxymethylase plays an important role in secretion of exportable material. Inhibition of pancreatic protein carboxymethylase activity in vivo may be one important mechanism by which ethionine interferes with digestive enzyme discharge.