SPHINGOMYELINASE-D ACTIVITY OF BROWN RECLUSE SPIDER (LOXOSCELES-RECLUSA) VENOM AS STUDIED BY P-31-NMR - EFFECTS ON THE TIME-COURSE OF SPHINGOMYELIN HYDROLYSIS

M. L, Merchant, J. F. Hinton and C. R. Geren. Sphingomyelinase D activ ity of brown recluse spider (Lososceles reclusa) venom as studied by P -31-NMR: effects on the time-course of sphingomyelin hydrolysis. Toxic on 36, 537-545, 1998.-The time-course for the hydrolysis of the D link age of chicken egg yolk sphingomyelin in a Triton X-100 mixed micelle and of lysophosphotidylcholine micelles, as catalyzed by brown recluse spider venom and brown recluse spider toxin, was followed by phosphor ous-31 nuclear magnetic resonance spectroscopy. The overall rate of hy drolysis of sphingomyelin in mixed micelles was found to be an order o f magnitude faster than the hydrolysis of lysophosphotidylcholine. Inc orporation of lysophosphotidylcholine into mixed micelles with Triton X-100 inhibited the lipase activity of brown recluse spider venom and brown recluse spider venom toxin. The effects of increased rates of ov erall reaction were observed with increased temperature and also with decreased ionic strength. The presence of divalent calcium ions was fo und to be necessary for hydrolytic activity, but only in catalytic amo unts (less than 1 mM), (C) 1998 Elsevier Science Ltd. Ail rights reser ved.