Chemistry And Biochemistry

A. General Relationships

All of the gastrointestinal hormones are polypeptides, and they are each produced in special endocrine cells that are dispersed throughout the stomach and small and large intestines. The gastrointestinal hormones were originally discovered during the search for physiological agents that regulated and stimulated the exocrine secretions and activities of the gut. Application of molecular biology techniques has resulted in significant advances with respect to the elucidation of the gene, cDNA, and, therefore, amino acid sequence of many GI hormones; also, for many of these hormones there is an emerging understanding of their membrane receptors and mode of signal transduction. As a consequence of these studies, it has been possible to identify structural homologies between the GI hormones and group them into families (see Table 8-4).

The discussion of the chemistry, biochemistry and biological actions of the GI hormones and neurotransmitters in the following sections follows their order of presentation in Tables 8-2 and 8-3.

B. Cholecystokinin (CCK)

1. Chemistry

A 115-amino-acid prepro form of cholecystokinin is cleaved to generate biologically active peptides of several sizes, including 59-, 38-, 33-, and 8-amino-acid

8. Gastrointestinal Hormones

0 0

Post a comment