固氮酶的结构 ■固氮酶复合物包括固氮酶和固氮酶还原酶。 固氮酶( dinitrogenase 两种肽链组成的四聚体:a2B2,活性中心在链 含有多个4Fe4 S centers和两个Mo- Fe clusters 称铁钼蛋白。 固氮酶还原酶( dinitrogenase reductase):由 两个相同的亚基组成,每个亚基含有一个Fe4-S4 redox center。又称铁蛋白 a The nitrogenase complex is highly conserved among different diazotrophs
固氮酶的结构 ◼ 固氮酶复合物包括固氮酶和固氮酶还原酶。 ◼ 固氮酶（ dinitrogenase ）： 两种肽链组成的四聚体：α2β2，活性中心在α链， 含有多个4Fe-4S centers 和两个 Mo-Fe clusters. 称铁钼蛋白。 ■固氮酶还原酶（ dinitrogenase reductase ）：由 两个相同的亚基组成，每个亚基含有一个Fe4 -S4 redox center。又称铁蛋白。 ◼ The nitrogenase complex is highly conserved among different diazotrophs
The nitrogenase complex consists of dinitrogenase and dinitrogenase redutase dinitrogenase(tetra dinitrogenase wpr FeMo protein dinitrogenase reductase(dimer) reductase(dimer or Fe pro t Fe-Mo cofactor 4Fe-4S ADP ADP 4Fe-4s 4Fe-4S (P-cluster) 4Fe-4S (P-cluster) ADP ADP (b) Fe-Mo cofactor
The nitrogenase complex consists of dinitrogenase and dinitrogenase redutase dinitrogenase (tetramer) or FeMo protein dinitrogenase reductase (dimer) or Fe protein dinitrogenase reductase (dimer) or Fe protein e - 4Fe-4S 4Fe-4S (P-cluster) Fe-Mo cofactor 4Fe-4S (P-cluster) 4Fe-4S ADP ADP ? Fe-Mo cofactor ADP ADP
N2 is believed to be reduced at the Fe-Mo cofactor Fe Fe Fe Fe Mor Molybdenum/N COO CH2 N/e e CHo HO→C—C00 CH2 cOo (c) Homocitrate
Molybdenum N2 is believed to be reduced at the Fe-Mo cofactor Fe Fe Fe Fe Fe Fe Fe S S S S S S S S S Mo
还原一分子N2需要8个电子 在固氮酶复合物上,消耗8个电子,将一分 子N2还原为2分子NH3,同时2个H被还原 为H2 电子来自于铁硫氧还蛋白( reduced ferredoxin, from photophosphorylation) x 黄素蛋白( reduced flavodoxin,from oxidative phosphorylation) 每传递一个电子需消化2个ATP,所释放的 能量用于改变固氮酶还原酶的构象,促进 电子的传递。 固氮酶的作用机制还不清楚,如固氮的同 时产生氢气的问题?
还原一分子N2需要8个电子 ◼ 在固氮酶复合物上，消耗8个电子，将一分 子N2还原为2分子NH3，同时2个H+被还原 为H2 . ◼ 电子来自于铁硫氧还蛋白(reduced ferredoxin， from photophosphorylation) 或 黄素蛋白 (reduced flavodoxin， from oxidative phosphorylation)。 ◼ 每传递一个电子需消化2个ATP，所释放的 能量用于改变固氮酶还原酶的构象，促进 电子的传递。 ◼ 固氮酶的作用机制还不清楚，如固氮的同 时产生氢气的问题？
coa+ 4CO9+ 4 pyruvate 4 acetyl-CoA Electrons are transferred to na bound in the 8 Ferredoxin or 8 Ferredoxin or 8 flavodoxin 8 flavodoxin active site of dinitrogenase (oxidized) (reduced) 8 via ferredoxin/ flavodoxin and dinitrogenase reductase 8 Dinitrogenase 8 Dinitrogenase reductase reductase (reduced) (oxidized) 16 ATP 16ADP +16P 8 Dinitrogenase 8 Dinitrogenase reductase (reduced reductase (oxidized +16ATP +16ATP 8 2H++2 2H++2e H+2 HH Dinitrogenase Dinitrogenase (oxidized) (reduced) N≡N→H-N=N-H→N一N 2NH3 HH 2NH H2 2H Diimine azine 4
Electrons are transferred to N2 bound in the active site of dinitrogenase via ferredoxin/flavodoxin and dinitrogenase reductase