Y-STC MKKIVFVLTLMLFSFGTLGQETASGQVGDVSSSTIATEVSEAECGTQSATTQGENDWDWCCELCCNPACFGC HSTC_YEREN Heat-stable enterotoxin C ystC 72 Toxin which activates the particulate form of guanylate cyclase and increases cyclic GMP levels within the host intestinal epithelial cells. Highly toxic.