(Science: protein) peptides found in the venoms of various snakes of the viper family, that inhibit the function of some integrins of the _1 and _3 classes. They were first identified as inhibitors of platelet aggregation and were subsequently shown to bind with high affinity to integrins and to block the interaction of integrins with RGD containing proteins for example they block the binding of the platelet integrin _IIb_3 to fibrinogen. Disintegrins are effective inhibitors at molar concentrations 500-2000x lower than short RGDX peptides. They are cysteine rich peptides ranging from 45 to 84 amino acids in length and almost all of them have a conserved RGD sequence on a _ turn, presumed to be the site that binds to integrins. The assumption is that their biological role in the venom is to inhibit blood clotting. Found in many snake species, where they are called variously albolabrin, applagin, batroxostatin, bitistatin, echistatin, elegantin, flavouridin, halysin, kistrin, triflavin and trigramin.