The membrane-associated c-type cytochromes(c-Cyts) have been well known as the key enzymes mediating extracellular electron transfer to terminal electron acceptors, resulting in biogeochemical elemental transformation...The membrane-associated c-type cytochromes(c-Cyts) have been well known as the key enzymes mediating extracellular electron transfer to terminal electron acceptors, resulting in biogeochemical elemental transformation, contaminant degradation, and nutrient cycling. Although c-Cyts-mediated metal reduction or oxidation have been mainly investigated with the purified proteins of metal reducing/oxidizing bacteria, the in vivo behavior of c-Cyts is still unclear, given the difficulty in measuring the proteins of intact cells. Fortunately, the in situ spectroscopy would be ideal for measuring the reaction kinetics of c-Cyts in intact cells under noninvasive physiological conditions. It can also help the establishment of kinetic/thermodynamic models of extracellular electron transfer processes, which are essential to understand the electron transfer mechanisms at the molecular scale. This review briefly summarizes the current advances in spectral methods for examining the c-Cyts in intact cells of dissimilatory metal reducing bacteria and Fe(Ⅱ)-oxidizing bacteria.展开更多
Laccases are blue copper oxidases （E.C. 1.10.3.2 benzenediol：oxygen oxidoreductase） that catalyze the one-electron oxidation of phenolics, aromatic amines and other electron-rich substrates with the concomitant red...Laccases are blue copper oxidases （E.C. 1.10.3.2 benzenediol：oxygen oxidoreductase） that catalyze the one-electron oxidation of phenolics, aromatic amines and other electron-rich substrates with the concomitant reduction of 02 to H20. They are currently seen as highly interesting industrial enzymes because of their broad substrate specificity. The Phanerochaete flavido-alba laccase is expressed and secreted as a soluble active enzyme by Aspergillus niger （rLac-LPFA）. rLac-LPFA is easily purified to homogeneity. Metal ions like HgCI2, KC12, FeSO4 and MgSO4 at a concentration of 2 mM have inhibiting effect on recombinant and native laccase, whereas, CuSO4 and MnSO4 moderately increase both enzyme activities. Two potential inhibitors （sodium azide and EDTA） inhibited enzyme activity, whereas, urea and SDS have no effect on enzyme activity. The Km and V,,ax values for recombinant laccase are 0.65 mM and 300 U/mg respectively for 2,6-DMP as substrate.展开更多
基金funded by the National Natural Science Foundations of China(41522105 and 41571130052)Guangdong Natural Science Funds for Distinguished Young Scholar(2014A030306041)Special Support Program(2016)
文摘The membrane-associated c-type cytochromes(c-Cyts) have been well known as the key enzymes mediating extracellular electron transfer to terminal electron acceptors, resulting in biogeochemical elemental transformation, contaminant degradation, and nutrient cycling. Although c-Cyts-mediated metal reduction or oxidation have been mainly investigated with the purified proteins of metal reducing/oxidizing bacteria, the in vivo behavior of c-Cyts is still unclear, given the difficulty in measuring the proteins of intact cells. Fortunately, the in situ spectroscopy would be ideal for measuring the reaction kinetics of c-Cyts in intact cells under noninvasive physiological conditions. It can also help the establishment of kinetic/thermodynamic models of extracellular electron transfer processes, which are essential to understand the electron transfer mechanisms at the molecular scale. This review briefly summarizes the current advances in spectral methods for examining the c-Cyts in intact cells of dissimilatory metal reducing bacteria and Fe(Ⅱ)-oxidizing bacteria.
文摘Laccases are blue copper oxidases （E.C. 1.10.3.2 benzenediol：oxygen oxidoreductase） that catalyze the one-electron oxidation of phenolics, aromatic amines and other electron-rich substrates with the concomitant reduction of 02 to H20. They are currently seen as highly interesting industrial enzymes because of their broad substrate specificity. The Phanerochaete flavido-alba laccase is expressed and secreted as a soluble active enzyme by Aspergillus niger （rLac-LPFA）. rLac-LPFA is easily purified to homogeneity. Metal ions like HgCI2, KC12, FeSO4 and MgSO4 at a concentration of 2 mM have inhibiting effect on recombinant and native laccase, whereas, CuSO4 and MnSO4 moderately increase both enzyme activities. Two potential inhibitors （sodium azide and EDTA） inhibited enzyme activity, whereas, urea and SDS have no effect on enzyme activity. The Km and V,,ax values for recombinant laccase are 0.65 mM and 300 U/mg respectively for 2,6-DMP as substrate.
