Leucostoma peptidase A: a metalloprotease from snake venom

binding as well as the change after binding which leads to the inhibitory effect . ß-BuTX did not reduce the store of actylcholine in the diaphragm even after complete neuromuscular blockade when the quantal content of end-plate potentials was markedly reduced. After neuromuscular blockade, bursts of miniature end-plate potentials could be evoked by hypertonicity or high K+ . It is concluded that the depression of the release of neurotransmitter by ß-BuTX is not due to depletion of the store, as previously postulated, but is due to an inhibition of the mechanism for releasing neurotransmitter . C.Y .

A. M., Fxmnucxs, K. K., Wnct~x, F. W. and Pxt~sco'rr, J. M. (Dept. Biochemistry and Biophysis, Texas A and M University, College Station, Texas, U.S .A .). Leucostoma Peptidase A: a metalloprotease from snake venom. Bicehim. biophys . Acta 293, 464, 1973 . SrlEx~f~v,

A PROTEOLYTIC enzyme (`Leucostoma Peptidase A') free of esterase and arylamidase activities was isolated from the venom of Agkistrodon pisclvorus leucostoma by ion exchange and gel chromatography. The enzyme has a pH optimum of pH 8~5 (substrate : hemoglobin) and a mol weight of 22,500. It hydrolyzes the polyaminoacid-derivatives of lysine, tyrosine, phenylalanine and tryptophane, several N-substituted dipeptides and the oxidised B-chain of insulin. The enzyme is not inhibited by serine specific reagents, but sensitive to o-phenanthroline and F.DTA . It is a metalloprotein containing two Ca'+ and one Zn'+ per molecule. All these characteristics-perhaps with exception of the molecular weight-indicate a similarity to metal chelator sensitive neutral professes, which so far have been isolated only from micro-organisms . H.M .

Rose, W. C., Btuot~r, S. G. and Lt:E, I. P. (Virginia Commonwealth University, Department of Microbiology, Richmond, Virginia, U.S .A .) . Potentiation of the toxicity of severalantitumor agents by SylmorttRa typhosa endotoxin. Toxic. appl . Pharmac. 23, 102, 1972 . i.n l or S. typhl endotoxin was combined with several antitumor agents. BALH/c mice were used and the administration was intraperitoneal. Lethality was observed up to one week . The endotoxin enhanced signi&antly the lethality of cyclophosphamide, daunomycin, methotrexate, polyI:C, procarbazine and vincristine. As man is very susceptible to endotoxin, the possible importance of these findings in man treated with antittmtor drugs iß discussed. H. R. AN

OXICON 1973 Yot. II