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Disintegrins , a family of polypeptides released in the venoms of viperid snakes ( vipers and rattlesnakes ) by the proteolytic processing of multidomain metalloproteinases , selectively block the function of beta ( 1 ) and beta ( 3 ) integrin receptors .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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