Carboxylmethylation of rat pancreatic acinar cell zymogen granule membrane proteins

Abstract

The protein carboxylmethylation reaction may be essential in the stimulus-secretion coupling phenomena of adrenal medulla, posterior pituitary and parotid (see Gagnon and Heisler, 1979). As a result of the reaction, methyl groups are transferred from S-adenosylmethionine (SAM) to negatively-charged carboxyl groups of protein substrates (MAP; methyl accepting proteins) by the enzyme protein carboxylmethylase (PCM). It has been hypothesized that neutralization of negative charges on MAP located on the surface of secretory vesicles may promote their movement toward and contact with the secretory pole of the cell and thereby may represent a preliminary step in the exocytotic pathway.

¹Supported by a Grant from the Medical Research Council of Canada. The assistance of Pat Ingalls in preparing the manuscript is gratefully acknowledged.