Purification And Effect Against Pests Of Ricin From Castor Beans

The ricin is a plant toxin that can be isolated from castor beans (Ricinus communis). The protein toxin has a molecular weight of about 64 000, which consists of two chains linked by a disulfide bond. Ricin A chain (RTA) is a ribosome-inactivating protein, whose molecular weight is about 31 000. Ricin B chain is the binding subunit and can specifically recognize receptors on the cell membrane, which have a terminal galactose. RTB molecular weight is about 34 000. The ricin enters into the cell through receptor-mediated endocytosis. RTA binds to protein L3 of ribosomal 60S subunit. It has specific N-glycosidase activity, and can catalytically cleave a specific adenine at the site of 4 234 out of the 28S rRNA. This cleavage of adenine can lead to the disruption of ribosomal function, thereby, inhibits the protein synthesis, and then cause the death of cells. For this reason, ricin has a good future for applying on anti-tumor and biological pesticide.Experimental methods and technology for the separation and purification of ricin from castor beans were described in this paper. By ammonium sulfate precipitation, Sepharose-4B affinity chromatography, and followed by molecular sieve chromato -graphy, purified ricin was obtained. The purified preparation showed two protein bands with relative molecular weights of 31 000 and 34 000. Effects of ricin and castor beans' raw extract against Pieris rapae (Linnaeus) larva and Myzws Persicae (Sulzer) were tested.The result showed that the ricin has a effect of contact toxicity on Pieris rapae (Linnaeus) larva, and it has few stomach toxicity effect. The ricinine has strong stomach and contact toxicity, and it also has strong antifeeding action against Pieris rapae (Linnaeus) larva.