Hiura H, Kakuno T, Yamashita J, Matsubara H, Horio T
J Biochem. 1981 Jun;89(6):1787-92. doi: 10.1093/oxfordjournals.jbchem.a133378.
When the photoheterotroph, Rhodospirillum rubrum, was grown in the light, ferredoxin was excreted from the cells in a significant amount, as well as hydrogenase. The extracellular ferredoxin was purified to a homogeneous state. The molecular weight was approximately 9,000, and the oxidation-reduction mid-potential was -0.29 V (N=1) at pH 7.0 and 25 degrees C. The amino acid composition was different from those of the intracellular ferredoxins, which were already known. The contents of non-heme iron and acid-labile sulfur were 10.6 and 7.9 mol/mol protein, respectively. The extracellular hydrogenase catalyzed the evolution of hydrogen gas from the ferredoxin in the reduced form. The Km for the ferredoxin was 4.1 micro M, one-seven hundredth as low as that for methyl viologen. There is a possibility that hydrogenase here were functional for evolution of hydrogen gas outside the cells.
当光合异养菌深红红螺菌在光照下生长时，铁氧化还原蛋白以及氢化酶会大量从细胞中排出。胞外铁氧化还原蛋白被纯化至均一状态。其分子量约为9000，在pH 7.0和25℃时氧化还原中点电位为-0.29 V（N = 1）。氨基酸组成与已知的胞内铁氧化还原蛋白不同。非血红素铁和酸不稳定硫的含量分别为10.6和7.9 mol/mol蛋白质。胞外氢化酶催化还原形式的铁氧化还原蛋白产生氢气。铁氧化还原蛋白的Km为4.1 μM，仅为甲基紫精的七百分之一。这里的氢化酶有可能在细胞外发挥产生氢气的功能。
