Toxin which activates the particulate form of guanylate cyclase and increases cyclic GMP levels within the host intestinal epithelial cells. Linaclotide is under clinical trial by Microbia to be used to improve bowel function in patients with chronic constipation. Linaclotide corresponds to residues 59 to 72 with Tyr-62. Belongs to the heat-stable enterotoxin family.