Chemical Studies on the Poison of Formosan Cobra. II

The Terminal Amino Acid Residues of Purified Poison (Neurotoxin)

Abstract

When the venom of Formosan cobra (Naja naja atra) is purified by acetone and ammonium sulfate, a strong poisonous component, that gives one spot moving towards the cathode side in paper electrophoresis, is obtained. It has almost no lecithinase action and its minimum lethal dose in mice is 0.08-0.1γ/g., causing respiratory paralysis. As tested by Sanger's DNP method and Akabori's hydrazinolysis method, its N-terminal amino acid was determined as leucine and its C-terminal amino acid as glycine. It was found from the formation of bis-dinitro-phenyl-aspartic and -glutamic acid α-monohydrazides during hydrazinolysis that the peptide chain contains aspartic acid with a free carboxyl group in the β-position and glutamic acid with free carboxyl group in the γ-position. The result of determination of these amino acids is given in Table I. Since these amino acids are present in one molecule each, the peptide composing this strong poisonous component is not branched and one mole each of aspartic and glutamic acids containing free carboxyl group are present in the peptide chain. From the content of these amino acids, the minimum molecular weight of this peptide is assumed to be around 6000. Cystine is not present as a terminal amino acid and it is clear that there is no cystine with a free carboxyl group in the peptide chain since there was no cystine derivatives in the sodium hydrogen carbonate layer during decomposition by Akabori's hydrazinolysis.