In article <Pine.HPP.3.96.990111194646.23225A-100000 at Nash.iupui.edu>,
<ricyoung at iupui.edu> wrote:
> Could anyone tell me what newsgroup I should direct this question to, or
> maybe someone here knows....
CCK is both a gut hormone and a neurotransmitter in the CNS, so this group
is as good as any.
> Is porcine cholecystokinin exactly structurally analogous to human CCK?
I suppose it depends on what you mean by CCK. This is a peptide which has a
number of forms which are biologically active. The full peptide is 58 amino
acids long (CCK-58). There are also 39, 33, 22 and 8 amino acid fragments
which are active (CCK-39, CCK-33 and CCK-22). What a lot of people refer to
as CCK is the 8 amino acid COOH terminal peptide CCK-8. All are produced
from processing of a large precurser, preprocholecystokinin. The last 5
amino acids are the same as the last 5 of gastrin, which accounts for the
partial agonism of CCK and gastrin.
The various length CCKs differ in their biological activity, the degree
depending on which function is being measured (pancreatic secretion or gall
bladder contraction) and which receptor subtype A or B is stimulated. In
*general* the shorter forms are more potent than the longer forms. But
there is some controversy over how great these differences are. In the
human, the most common forms released from the intestine after a meal are
probably CCK-33 and CCK-8 and some CCK-58 and CCK-22.
Human CCK-8 and porcine CCK-8 (as well as dog, rat, mouse and sheep) all
have the same sequence. That is, there is one mammalian CCK-8. But the
sequences of human and porcine differ slightly for the longer forms. There
is 1 amino acid difference between human and pig in CCK-22, 3 in CCK-33, 4
in CCK-39 and 10 in CCK-58. See Walsh in Chapter 1 of The Physiology of the
Gastointestinal Tract, Johnson et al (eds.) 3rd Ed, Raven Press, 1994 for a
good review of the GI hormones.
> Would porcine cholecystokinin become antigenic after intramuscular
> administration? If so, is there a comercially available recombinant CCK>?
It's unlikely that porcine CCKs would be antigenic, but it can happen as
with porcine insulin (but people have also developed allergic reactions to
human insulin). Tell me, why would you want to take CCK? Are you thinking
of its use as an appetite suppressant? You do know that it can provoke
panic attacks, don't you?
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