caa a22 4500 475744438 CHVBK 20180406123509.0 cr unu---uuuuu 170329e20001101xx s 000 0 eng 10.1023/A:1007100319108 doi (NATIONALLICENCE)springer-10.1023/A:1007100319108 Effect of Redox Mediators on Nitrogenase and Hydrogenase Activities in Azotobacter vinelandii [Elektronische Daten] [H. Huang, Q. Lin, W. Zhai, C. Chen] In bioelectrochemical studies, redox mediators such as methylene blue, natural red, and thionine are used to studying the redox characteristics of enzymes in the living cell. Here we show that nitrogenase activity in Azotobacter vinelandii is completely inhibited by oxidized methylene blue (MBo) when the concentration of this mediator in the medium is increased up to 72 μM. This activity in A. vinelandii is somewhat inhibited by a coenzyme, ascorbic acid (AA). However, the nitrogenase activity within the A. vinelandii cell is unchanged even for a high concentration of oxidized natural red (NRo) alone. Interestingly, these mediators and AA do not have the capacity to inhibit the H2 uptake activity of the hydrogenase in A. vinelandii. Average active rates of 66 nM H2 evolved/mg cell protein/min from the nitrogenase and 160 nM H2-uptake/mg cell protein/min from the hydrogenase in A. vinelandii are found in aid of the activities of the enzymes for H2 evolution and for H2 uptake are compared. The activities of both enzymes in A. vinelandii are strongly inhibited by thionine having high oxidative potential. Mechanisms of various mediators acting in vivo for both enzymes in A. vinelandii are discussed. Plenum Publishing Corporation, 2000 Azotobacter vinelandii nationallicence nitrogenase activity nationallicence hydrogenase activity nationallicence redox mediators nationallicence H2 evolution and uptake nationallicence redox potential nationallicence electron transfer chain nationallicence Huang H. School of Life Sciences, Xiamen University, 361005, Xiamen, China aut Lin Q. The Research Center of Environment Science, Xiamen University, 361005, Xiamen, China aut Zhai W. School of Life Sciences, Xiamen University, 361005, Xiamen, China aut Chen C. Institute of Molecular and Cell Biology, National University of Singapore, 117609, Singapore aut Journal of Protein Chemistry Kluwer Academic Publishers-Plenum Publishers 19/8(2000-11-01), 671-678 0277-8033 19:8<671 2000 19 10930 https://doi.org/10.1023/A:1007100319108 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1007100319108 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Huang H. School of Life Sciences, Xiamen University, 361005, Xiamen, China aut NATIONALLICENCE 700 1- Lin Q. The Research Center of Environment Science, Xiamen University, 361005, Xiamen, China aut NATIONALLICENCE 700 1- Zhai W. School of Life Sciences, Xiamen University, 361005, Xiamen, China aut NATIONALLICENCE 700 1- Chen C. Institute of Molecular and Cell Biology, National University of Singapore, 117609, Singapore aut NATIONALLICENCE 773 0- Journal of Protein Chemistry Kluwer Academic Publishers-Plenum Publishers 19/8(2000-11-01), 671-678 0277-8033 19:8<671 2000 19 10930 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer