Processing of chromogranin A within chromaffin granules starts at C‐ and N‐terminal cleavage sites

Specific antisera were raised against synthetic peptide fragments of bovine chromogranin A. The soluble proteins of bovine chromaffin granules were subjected to two-dimensional immunoblotting with these antisera. The endogenous breakdown products of chromogranin A gave distinct patterns of immunostaining which enabled us to correlate these peptides with defined regions of the chromogranin A molecule. The results establish that within chromaffin granules degradation of chromogranin A by the endogenous proteases can start either at the C- or the N-terminal site.