title: Effects of metal ions on the conformation and activity of acutolysin D from Agkistrodon Acutus venom.
abstract: Acutolysin D, isolated from the venom of Agkistrodon acutus, possesses marked haemorrhagic and proteolytic activities. The molecular weight and the absorption coefficients (A (1%) (280)) of acutolyisn D have been determined to be 47,850 +/- 8 amu and 9.3 by mass spectrometer and UV spectrum, respectively. The effects of metal ions on the conformation and activity of acutolysin D have been studied by following fluorescence, circular dichroism and biological activity measurements. Acutolysin D contains two Ca(2+)-binding sites and two Zn(2+)-binding sites determined by atomic absorption spectrophotometer. Zn(2+) is essential for the enzyme activities of acutolysin D, however, the presence of 1 mM Zn(2+) significantly decreases its caseinolytic activity and intrinsic fluorescence intensity at pH 9.0 due to Zn(OH)(2) precipitate formation. Ca(2+) is important for the structural integrity of acutolysin D, and the presence of 1 mM Ca(2+) markedly enhances its caseinolytic activity. Interestingly, the caseinolytic activity which is inhibited partly by Cu(2+), Co(2+), Mn(2+) or Tb(3+) and inhibited completely by Cd(2+), is enhanced by Mg(2+). The fluorescence intensity of the protein decreases in the presence of Cu(2+), Co(2+), Cd(2+) or Mn(2+), but neither for Ca(2+), Mg(2+) nor for Tb(3+). Zn(2+), Ca(2+), Mg(2+), Cu(2+), Mn(2+), Co(2+ )and Tb(3+) have slight effects on its secondary structure contents. In addition, Cd(2+) causes a marked increase of antiparallel beta-sheet content from 45.5% to 60.2%.
authors.affiliation: Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, PR China. xuxl@ustc.edu.cn
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Xu
authors.forename: Xianghu
authors.initials: X
authors.lastname: Liu
authors.forename: Liyun
authors.initials: L
authors.lastname: Zhang
authors.forename: Jiexia
authors.initials: J
authors.lastname: Chen
authors.forename: Wenqi
authors.initials: W
authors.lastname: Liu
authors.forename: Qingliang
authors.initials: Q
authors.lastname: Liu
mesh_terms: D017836:Agkistrodon / Q000378:metabolism*; D000818:Animals; D002104:Cadmium / Q000737:chemistry / Q000494:pharmacology; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry / Q000494:pharmacology; D003435:Crotalid Venoms / Q000378:metabolism; D008670:Metals / Q000737:chemistry* / Q000494:pharmacology; D008970:Molecular Weight; D011487:Protein Conformation / Q000187:drug effects; D012910:Snake Venoms / Q000737:chemistry* / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D015032:Zinc / Q000737:chemistry / Q000494:pharmacology
chemical_list: D003435:Crotalid Venoms; D008670:Metals; D012910:Snake Venoms; C488502:acutolysin D, Agkistrodon; D002104:Cadmium; D003300:Copper; D015032:Zinc