[Study of the effect of Pb2+ on alpha-amylase activity by spectroscopy].
The activity of alpha-amylase from porcine pancreas was enhanced under the treatment by Pb2+ at low concentration (0.5-4 mumol.L-1), but was inhibited by Pb2+ at high concentration (above 4 mumol.L-1). Pb2+ at high concentration could competitively displace Ca2+ from alpha-amylase. The EXAFS demonstrated that Pb2+ was bound to the active site of alpha-amylase, the coordination atom was oxygen, the coordination number was 2, and the Pb-O bond length was 0.234 nm. Circular dichroism spectra showed that the secondary structure of trypsin was greatly changed by Pb2+ at high concentration, as alpha-helix, beta-turn and random coil contents decreased, while beta-sheet, aromatic and disulfide bond contents increased. It was suggested that Pb2+ was bound to result in an alpha-amylase conformational change, and the enzyme activity decreased.
Hong
Fa-shui
FS
College of Life Sciences, Suzhou University, Suzhou 215006, China.
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002118:Calcium / Q000737:chemistry; D004577:Electron Probe Microanalysis / Q000379:methods; D007854:Lead / Q000494:pharmacology*; D010100:Oxygen / Q000737:chemistry; D010179:Pancreas / Q000201:enzymology; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence / Q000379:methods; D013552:Swine; D000516:alpha-Amylases / Q000737:chemistry / Q000378:metabolism*
D007854:Lead; D000516:alpha-Amylases; D010100:Oxygen; D002118:Calcium