尖吻蝮(Agkistrodon acufus)蛇毒凝血酶样成分的研究 Ⅱ: 酶学与血液学活性的研究

对尖吻蝮蛇毒四个凝血酶样成分(TLP)的酶学性质的比较研究表明,它们都具有凝结(血)活性和精氨酸酯酶活性。其凝结活力TLP_(4)>TLP_(3 )>TLP_(1)>TLP_(2),Ca~(++)有激活作用,但不被肝素、EDTA所抑制; 精氨酸酯酶活力以TLP_(1)、TLP_(2)较高, Ca~(++)、EDTA无明显的激活或抑制作用;TLP_(1)对热比较稳定,TLP_(4)对于酸碱变化比较稳定。经动物体内试验表明,尖吻蝮蛇毒与美洲矛头蝮蛇毒一样,同时含有去纤酶和蛇毒凝血酶。图1表3参9

尖吻蝮(Agkistrodon acutus)蛇毒凝血酶样成分的研究Ⅲ:蛇毒凝血酶止血效应的研究

将纯化的蛇毒凝血酶(TLE_(3)、TLE_(4)), 经家免试验表明, 2—3凝血酶单位/kg体 重剂量能显著地使家兔全血凝血时间短1/3—1/2。药后1h即有促凝作用, 以2—4h凝血(止血)效应最强, 12h已消失。经家兔及家犬实验性创伤止血实验表明, 对创伤出血有止血作用。表2参11

CHARACTERIZATION OF OHS1, AN ARGININE/LYSINE AMIDASE FROM THE VENOM OF KING COBRA (OPHIOPHAGUS HANNAH)

In this paper, we present the results of purification and characterization of an arginine/lysine amidase from the venom of Ophiophagus hannah (OhS1). It was purified by Sephadex G-75 gel filtration and ion-exchange chromatography on DEAE-Sepharose CL-6B. It is a protein of about 43,000, consisting of a single polypeptide chain. It is a minor component in the venom. The purified enzyme was capable of hydrolysing several tripeptidyl-p-nitroanilide substrates having either arginine or lysine as the C-terminal residue. We studied the kinetic parameters of OhS1 on six these chromogenic substrates. OhS1 did not clot fibrinogen. Electrophoresis of fibrinogen degraded with OhS1 revealed the disappearance of the alpha- and beta-chains and the appearance of lower mel. wt fragments. OhS1 had no hemorrhagic activity. It did not hydrolyse casein, nor did it act on blood coagulation factor X, prothrombin and plasminogen. The activity of OhS1 was completely inhibited by NPGB, PMSF, DFP, benzamidine and soybean trypsin inhibitor, suggesting it is a serine protease. Metal chelator (EDTA) had no effect on it.

Structure-function relationship of three neurotoxins from the venom of Naja kaouthia: a comparison between the NMR-derived structure of NT2 with its homologues, NT1 and NT3

Three homologous short-chain neurotoxins, named NT1, NT2 and NT3, were purified from the venom of Naja kaouthia. NT1 has an identical amino acid sequence to cobrotoxin from Naja naja atra [Biochemistry 32 (1993) 2131]. NT3 shares the same sequence with cobrotoxin b [J. Biochem. (Tokyo) 122 (1997) 1252], whereas NT2 is a novel 6 1 -residue neurotoxin. Tests of their physiological functions indicate that NT1 shows a greater inhibition of muscle contraction induced by electrical stimulation of the nerve than do NT2 and NT3. Homonuclear proton two-dimensional NMR methods were utilized to study the solution tertiary structure of NT2. A homology model-building method was employed to predict the structure of NT3. Comparison of the structures of these three toxins shows that the surface conformation of NT1 facilitates the substituted base residues, Arg28, Arg30, and Arg36, to occupy the favorable spatial location in the central region of loop 11, and the cation groups of all three arginines face out of the molecular surface of NT1 This may contribute greatly to the higher binding of NT1 with AchR compared to NT2 and NT3. (C) 2002 Elsevier Science B,V. All rights reserved.