Gastrointestinal Health

Guanylin

Guanylin is how the intestine decides how wet it is: it activates guanylate cyclase C on the cells lining the gut, cyclic GMP rises, chloride channels open and fluid follows. Two drugs sold for constipation, linaclotide and plecanatide, act at that same receptor, and that is where guanylin's practical importance lies — it is the template, not the medicine, and has never been given to a person as a treatment. The record's evidence tier rests on an animal study in fish, four of its seven references are reviews, and the landmark on file is still the 1992 paper that purified the peptide out of rat intestine.

Last updated 12 August 2026

Studied forIntestinal fluid research · Constipation therapy context · Guanylate cyclase C research

Evidence on file2 animal studies · 1 in-vitro study

Strongest sourceGuanylin: an endogenous activator of intestinal guanylate cyclase (Proceedings of the National Academy of Sci… (animal study)

Mechanism

Activates guanylate cyclase C on enterocytes, raising cyclic GMP and opening CFTR chloride channels to drive fluid secretion.

Reported effects

What sources associate with this compound. Reported categories, not outcomes we have graded — each would need its own citation and rung.

Intestinal fluid research
Constipation therapy context
Guanylate cyclase C research

Dosing on file unverified

No established human dose; SP-304 analog: 3-9 mg/day in trials

Carried from a source that labels it unverified, and reproduced with that label attached. A record of what is reported, not a recommendation. No citation on this page establishes it.

Literature on file 7

animal in vivo
Guanylin: an endogenous activator of intestinal guanylate cyclase (Proceedings of the National Academy of Sciences 1992, cited 431x) graded on: an animal model — read from the indexed abstract — “rats”
review or editorial
Uroguanylin and guanylin peptides: pharmacology and experimental therapeutics (Pharmacology & Therapeutics 2004, cited 134x) graded on: indexed as "Review" - secondary literature, not a study — “Review”
review or editorial
Linaclotide for irritable bowel syndrome with constipation: integrating realworld evidence into the therapeutic puzzle. graded on: indexed as "Review" - secondary literature, not a study — “Review”
review or editorial
Gut reactions and gut instincts: regulation of intestinal homeostasis by receptor guanylyl cyclase C (GC-C). graded on: indexed as "review-article" - secondary literature, not a study — “review-article”
review or editorial
Membrane Guanylyl Cyclases as Potential Targets for Guanylin Action. graded on: indexed as "Review" - secondary literature, not a study — “Review”
animal in vivo
Symbiotic bacteria may support calcium carbonate precipitation in the Gulf toadfish. graded on: Gulf toadfish salinity treatments with gut microbiome and meta-transcriptomic analysis — read from the abstract — “abstract review”
in vitro
MUC1-Driven Guanylin Gene Delivery via Succinylated PEI-9 Nanocarrier for Colorectal Cancer Treatment: An in Silico and In vitro Study. graded on: an in-vitro system — “In vitro”

Identity

Space-filling 3D model of Guanylin, carbon grey, nitrogen blue, oxygen red — Built from the SMILES on this record — the atoms and bonds are exact. The shape is **one computed low-energy pose**, not a measured structure: a flexible peptide in solution has no single conformation, and where the SMILES leaves a stereocentre undefined the pose commits to one arbitrarily. The skeletal formula below claims connectivity and nothing more, which is what we actually know.

2D chemical structure of Guanylin — Built from the SMILES on this record — the atoms and bonds are exact. The shape is **one computed low-energy pose**, not a measured structure: a flexible peptide in solution has no single conformation, and where the SMILES leaves a stereocentre undefined the pose commits to one arbitrarily. The skeletal formula below claims connectivity and nothing more, which is what we actually know.

Molecular weight: 1519.8
Molecular formula: C60H94N16O22S4
CAS number: 140653-38-9
PubChem CID: 5489468
UniProt: Q02747 (precursor)
InChI key: SULKGYKWHKPPKO-RAJPIYRYSA-N
Sequence: PNTCEICAYAACTGC
SMILES: CC[C@H](C)[C@@H](C(=O)N[C@@H](CS)C(=O)N[C@@H](C)C(=O)N[C@@H](CC1=CC=C(C=C1)O)C(=O)N[C@@H](C)C(=O)N[C@@H](C)C(=O)N[C@@H](CS)C(=O)N[C@@H]([C@@H](C)O)C(=O)NCC(=O)N[C@@H](CS)C(=O)O)NC(=O)[C@H](CCC(=O)O)NC(=O)[C@H](CS)NC(=O)[C@H]([C@@H](C)O)NC(=O)[C@H](CC(=O)N)NC(=O)[C@@H]2CCCN2
InChI: InChI=1S/C60H94N16O22S4/c1-8-25(2)44(74-51(88)34(15-16-43(82)83)68-55(92)38(22-100)73-59(96)46(30(7)78)76-53(90)36(19-41(61)80)70-50(87)33-10-9-17-62-33)58(95)72-37(21-99)54(91)66-28(5)48(85)69-35(18-31-11-13-32(79)14-12-31)52(89)65-26(3)47(84)64-27(4)49(86)71-39(23-101)56(93)75-45(29(6)77)57(94)63-20-42(81)67-40(24-102)60(97)98/h11-14,25-30,33-40,44-46,62,77-79,99-102H,8-10,15-24H2,1-7H3,(H2,61,80)(H,63,94)(H,64,84)(H,65,89)(H,66,91)(H,67,81)(H,68,92)(H,69,85)(H,70,87)(H,71,86)(H,72,95)(H,73,96)(H,74,88)(H,75,93)(H,76,90)(H,82,83)(H,97,98)/t25-,26-,27-,28-,29+,30+,33-,34-,35-,36-,37-,38-,39-,40-,44-,45-,46-/m0/s1

Notes unverified prose

Phase II for chronic constipation (SP-304); preclinical; no FDA approval; Phase II (SP-304, chronic constipation)

Not on file 1

All 8 tracked fields hold a value on this record. 1 further absence is named below. A blank field is a bug; a named absence is a finding.

half-lifenothing we hold supplies it

Each field links to every other record missing the same thing. The full ledger holds 765 gaps across 163 records.