[Post-translational maturation of peptides of the glucagon family. Relationship with their mode of action].

Two types of proglucagon processing have been evidenced in producing tissues (endocrine pancreas, stomach, intestine, central nervous system) using antibodies recognizing the epitopes unmasked during processing, which takes place at dibasic sites. A first type, leading essentially to glucagon, has been observed in the two former tissues; a second type, leading to peptides (oxyntomodulin and glicentin) containing an additional C-terminal octapeptide, has been shown in the two latter. All peptides are released in plasma and reach their targets: liver, fat... (control of metabolism) for glucagon and gastric mucosa (control of acid secretion) for the octapeptide-bearing peptides. The mode of action of these peptides includes receptors coupled to adenylate cyclase and a processing, at a dibasic site, of the circulating peptides leading to C-terminal fragments which act through non cyclic AMP-dependent mechanisms, such as the control of the plasma membrane calcium pump.