Nelson L M, Salminen S O
J Bacteriol. 1982 Aug;151(2):989-95. doi: 10.1128/jb.151.2.989-995.1982.
The role of uptake hydrogenase was studied in Rhizobium leguminosarum bacteroids from the nodules of Pisum sativum L. cv. Homesteader. Uptake hydrogenase activity, measured by the 3H2 uptake method, was dependent on O-consumption and was similar to H2 uptake measured by gas chromatography. Km for O2 of 0.0007 atm (0.0709 kPa) and a Km for H2 of 0.0074 atm (0.7498, kPa) were determined. H2 increased the rate of endogenous respiration by isolates with uptake hydrogenase (Hup+) but had no effect on an isolate lacking uptake hydrogenase (Hup-). A survey of 14 Hup+ isolates indicated a wide range of H2 uptake activities. Four of the isolates tested had activities similar to or higher than those found in two Hup+ Rhizobium japonicum strains. H2 uptake was strongly coupled to ATP formation in only 5 of the 14 isolates. H2 increased the optimal O2 level of C2H2 reduction by 0.01 atm and permitted enhanced C2H2 reduction at O2 levels above the optimum in both a coupled and an uncoupled isolate. At suboptimal O2 concentrations a small enhancement of C2H2 reduction by H2 was seen in two out of three isolates in which H2 oxidation was coupled to ATP formation. Thus, the main function of uptake hydrogenase in R. leguminosarum appears to be in the protection of nitrogenase from O2 damage.
对来自豌豆（Pisum sativum L. cv. Homesteader）根瘤的豌豆根瘤菌类菌体中摄取氢化酶的作用进行了研究。通过³H₂摄取法测定的摄取氢化酶活性依赖于氧气消耗，且与气相色谱法测定的H₂摄取相似。测定了氧气的Km为0.0007 atm（0.0709 kPa），氢气的Km为0.0074 atm（0.7498 kPa）。氢气增加了具有摄取氢化酶（Hup⁺）的分离株的内源性呼吸速率，但对缺乏摄取氢化酶的分离株（Hup⁻）没有影响。对14个Hup⁺分离株的调查表明，H₂摄取活性范围很广。所测试的分离株中有4个的活性与两种日本根瘤菌Hup⁺菌株相似或更高。在14个分离株中，只有5个的H₂摄取与ATP形成紧密偶联。氢气使乙炔还原的最佳氧气水平提高了0.01 atm，并使偶联和非偶联分离株在高于最佳氧气水平时的乙炔还原增强。在次最佳氧气浓度下，在三个H₂氧化与ATP形成偶联的分离株中，有两个观察到氢气对乙炔还原有小幅增强作用。因此，豌豆根瘤菌中摄取氢化酶的主要功能似乎是保护固氮酶免受氧气损伤。
