PURIFICATION, CHARACTERIZATION, AND AMINO-ACID-SEQUENCE DETERMINATIONOF ACANTHINS, POTENT INHIBITORS OF PLATELET-AGGREGATION FROM ACANTHOPHIS-ANTARCTICUS (COMMON DEATH ADDER) VENOM

Venom of Acanthophis antarcticus, a common death adder, exhibits poten t antiplatelet effects. By a combination of gel-filtration, cation-exc hange, and reversed-phase chromatographic methods, two inhibitors of p latelet aggregation, named acanthin I and II, were purified to homogen eity as assessed by capillary electrophoresis and electrospray mass sp ectrometry, These isoforms exhibit the most potent antiplatelet activi ty known thus far, with IC,, values of 7 nM. for acanthin I and 4 nM f or acanthin II in human whole blood when collagen was used as an agoni st, whereas with ADP the IC,, values were PO and 12nM, respectively. A canthin I and II are basic proteins with pIs of 10.2 +/- 0.1 and 10.4 +/- 0.1 and molecular weights of 12,844.58 +/- 0.61 and 12,895.63 +/- 0.48, respectively, as determined by electrospray mass spectrometry. T hey exhibit phospholipase enzyme activity, and acanthin I and II hydro lyzed 51.57 +/- 1.30 and 46.85 +/- 2.90 pmol of phatidylcholine/min/mg , respectively. The complete amino acid sequences of acanthin I and II showed that they have a high homology with each other and with other elapids' phospholipase A, neurotoxin, especially pseudexin A, (C) 1998 Academic Press.