title: Biochemical and pharmacological properties of a new thrombin-like serine protease (Russelobin) from the venom of Russell's Viper (Daboia russelii russelii) and assessment of its therapeutic potential.
abstract: BACKGROUND
  Snake venoms are rich sources of bioactive molecules, and several venom-derived proteins have entered clinical trials for use in ischemic disorders; however, late-stage failure of a recent drug candidate due to low in vivo efficacy demonstrated the need for new sources of fibrinogenolytic drug candidates.
  
  
  METHODS
  A 51.3kDa thrombin-like serine protease (Russelobin) purified from the venom of Russell's Viper (Daboia russelii russelii) was subjected to extensive biochemical characterization, including N-terminal sequencing, substrate specificity, kinetic and inhibitor assays, glycosylation analysis and stability assays. Toxicity and pathology analyses were conducted in NSA mice.
  
  
  RESULTS
  Russelobin has extensive N-terminus identity with a beta-fibrinogenase-like serine proteinase precursor from Daboia russelii siamensis venom, a mass of 51.3kDa and contains extensive N-linked oligosaccharides. Serine protease inhibitors and heparin significantly decreased activity, with much lower inhibition by DTT, antithrombin-III and α2-macroglobulin. Russelobin preferentially released FPA and slowly released FPB from human fibrinogen, forming a labile fibrin clot readily hydrolyzed by plasmin. The partially deglycosylated enzyme showed significantly lower activity toward fibrinogen and less resistance against neutralization by plasma α2MG and antithrombin-III. Russelobin was non-cytotoxic, non-lethal and produced no histopathologies in mice, and it demonstrated in vivo dose-dependent defibrinogenating activity.
  
  
  CONCLUSIONS
  Russelobin is an A/B fibrinogenase with high specificity toward fibrinogen, both in vitro and in vivo. Extensive glycosylation appears to protect the molecule against endogenous protease inhibitors, prolonging its in vivo efficacy.
  
  
  CONCLUSIONS
  Due to its low toxicity, stability and activity as a defibrinogenating agent, Russelobin shows high potential for cardiovascular drug development.
authors: School of Biological Sciences, University of Northern Colorado, Greeley, CO 80639-0017, USA.
authors: Ashis K
authors: AK
authors: Mukherjee
authors: Stephen P
authors: SP
authors: Mackessy
mesh_terms: D000818:Animals; D005340:Fibrinogen / Q000737:chemistry / Q000378:metabolism; D005343:Fibrinolytic Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D006801:Humans; D008116:Lizards; D008297:Male; D051379:Mice; D008970:Molecular Weight; D017840:Daboia; D057057:Serine Proteases / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000494:pharmacology; D014757:Viper Venoms / Q000201:enzymology*
chemical_list: D005343:Fibrinolytic Agents; D015842:Serine Proteinase Inhibitors; D014757:Viper Venoms; D005340:Fibrinogen; D057057:Serine Proteases