FIGURE 8-7 Organization of preprosecretin. [The information was abstracted from Kopin, A. S., Wheeler, M. B., and Leiter, A. B. (1990). Secretin: Structure of the precursor and tissue distribution. Proc. Nat. Acad. Sei. USA 87, 2299-2303.]
Preprosecretin tide. GIP, which is a member of the secretin peptide family (Table 8-4), shares a high sequence homology with both glucagon (15 amino acids identical) and secretin (9 amino acids identical) (see Figure 8-6). GIP is biosynthesized largely by K cells present in the small intestine. Receptors for GIP have been identified in selected regions of the GI tract as well as the brain.
Little information is available concerning the mechanisms by which GIP elicits biological responses. Two categories of biological responses are known: (i) inhibition of gastric acid secretion and gastric motility and (ii) potentiation of pancreatic insulin secretion after oral as opposed to intravenous glucose administration.
Motilin is a 22-amino-acid linear peptide (see Figure 8-8); the biological activity is believed to be associated with the nine N-terminal residues. The amino acid sequence is entirely different from that of all other known gastrointestinal hormones. The solution structure of motilin has been determined in detail via nuclear magnetic resonance (NMR) studies.
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All you need is a proper diet of fresh fruits and vegetables and get plenty of exercise and you'll be fine. Ever heard those words from your doctor? If that's all heshe recommends then you're missing out an important ingredient for health that he's not telling you. Fact is that you can adhere to the strictest diet, watch everything you eat and get the exercise of amarathon runner and still come down with diabetic complications. Diet, exercise and standard drug treatments simply aren't enough to help keep your diabetes under control.