Two　trypsin　inhibitors　and　one　chymotrypsin　inhibitor　from　Chinese　Daboia　russellii　siamensis　venom,　denoted　as　CBPTI-1,　CBPTI-2　and　CBPTI-3　were　purified,　characterized　and　cloned　from　lyophilized　venom-derived　cDNA　libraries.　The　N-terminus　of　CBPTI-1　was　modified　and　not　amenable　to　Edman　degradation　sequencing,　however　an　internal　partial　sequence　was　found　to　be　SGRCRGHLRRIYYNPDSNKCE.　The　N-termini　of　CBPTI-2　and　CBPTI-3　were　unmodified　and　their　partial　sequences　were　established　as　HDRPTFCNLAPESGRCRAH　and　HDRPKFCYLPADPGECMAYIRSFYYDS　respectively.　From　cloning　studies　CBPTI-1　was　found　to　consist　of　66　amino　acid　residues,　while　CBPTI-2　and　CBPTI-3　precursors　consist　of　60　amino　acid　residues,　including　6　cysteine　residues.　Another　cDNA　sequence　(CBPTI-4)　was　also　obtained.　Alignment　of　cDNA　sequences　showed　that　CBPTI-3　exhibited　similar　sequence　homology　to　CBPTI-4　cDNA　except　for　an　8　nucleotide　deletion　in　the　open-reading　frame.　CBPTI-1　and　CBPTI-2　were　demonstrated　to　be　potent　trypsin　inhibitors,　but　were　also　shown　to　be　effectively　potent　in　chymotrypsin　inhibition.　The　K-i　values　of　CBPTI-1　and　CBPTI-2　for　typsin　inhibition　were　4.07　x　10(-7)　M　and　6.66　x　10(-7)　M,　respectively,　and　they　were　non-competitive　in　their　activity.　CBPTI-3　showed　chymotrypsin　inhibition　activity　with　a　K-i　value　of　2.55　x　10(-9)　M,　but　did　not　show　trypsin　inhibitor　activity.　(c)　2013　Elsevier　Ltd.　All　rights　reserved.