Effects of metal ions and an inhibitor on the fluorescence and activity of acutolysin A from Agkistrodon acutus venom.

Acutolysin A, a protein isolated from the venom of Chinese Five-pace snake (Agkistrodon acutus) has shown marked hemorrhagic and proteolytic activities. In the present study, the effects of metal ions and an inhibitor EDTA on the fluorescence and function of autolysin A have been studied, by following fluorescence and activity measurements. Acutolysin A contains a Ca(2+)-binding site, which provides it with important structural stability, and a Zn(2+)-binding site, which is essential for its enzymatic activities. The removal of metal ions in acutolysin A by incubation with EDTA results in irreversible inhibition and complete denaturation, and a marked decrease in its fluorescence intensity. The fluorescence intensity of acutolysin A is also decreased in the presence of Cu2+, Co2+, Mn2+ or Mg2+, but does not change in the presence of Ca2+, Cd2+, or Tb3+. Caseinolytic activity of acutolysin A is enhanced by Co2+, Ca2+ and Mg2+, but is partly inhibited by Cu2+, Mn2+ and Tb3+, and completely inhibited by Cd2+. Both Zn2+ and Co2+ recover the loss of activity of the protein caused by Cd2+.