【摘要】 固氮鱼腥藻（水生686）整体水平在光照下同时有释氢和放氧的现象。氢的释放量与乙炔还原活性有平行的关系。在暗期,释氢量极少。 固氮鱼腥藻在光照下具有较强的吸氢作用,这是由于氢酶有吸氢的特性。我们看到H₂和O₂的浓度对氢酶的活性有一定的影响。氢酶催化分子氢和分子氧的反应的Km值分别为1.6mM和0.5mM。 分子氢能明显地支持乙炔还原作用,当以空气为气相的反应体系中含有10％分子氢时,大大地提高乙炔还原的活性。 铵离子不仅抑制乙炔还原,而且对释氢作用也有明显的抑制。随着铵离子浓度的增加抑制作用愈为显著。当铵离子浓度达到10mM时,乙炔还原和释氢都几乎全被抑制。说明放氢与固氮酶的活性有密切的联系。 DCMU(2×10^-5M)对乙炔还原活性和释氢的抑制约20％,DNP(5×10^-4M)表现出更强烈的抑制。更多还原

【Abstract】 Anabaena azotica Ley HB 686, which is native to China, has been selected for the study of nitrogen fixation and hydrogen evolution. In the present investigation the following phenomena have been observed:1. Under illumination （20,000 lux） the acetylene reduction and the evolution of hydrogen and oxygen by the filaments of blue-green algae A. azotica HB 686 increase with time. In darkness the H₂-evolution is much less. It is shown that the H₂-production is light-dependent. Although the production of both C₂H₄ and O₃ is linear, that of O₂ has a higher rate. It is highly probable that the rate of photosynthesis is higher than that of nitrogen fixation.A. azotica contains hydrogenase which catalyses the consumption of H₂. Under illumination in the beginning 2 hours, the consumption of H₂ increases with time. Afterward it comes to a smooth plateau. It may be supposed that the H, released by nitrogenase combines with the O₂ released from photosystem Ⅱ. Besides, H₂ consumption by A. azotica in darkness is also much lower. This demonstrates that light is necessary for the consumption of H₂.2. The characteristics of hydrogen consumption catalyzed by hydrogenase have been studied. Argon has been used as gas phase which contained 4% H₂ and various concentrations of O₃. When O₂ concentration is lower than 2 %, the rate of consumption of H₂ increases with an increase of O₂ concentration, while with 4% O₂ the consumption of H₂ does not increase. The Km of hydrogenase for oxygen is 0.5 mM.The concentration of H₂ affects the rate of hydrogen consumption significantly. The Km of hydrogenase for hydrogen is 1.6 mM.3. The activity of acetylene reduction may be enhanced when the gas phase contains 10% H₂. Itis probable that the Knallgas reaction can utilize the excess oxygen and thereby keep the nitrogenase under anaerobic condition and protect the enzyme within the cell.4. Various concentrations of ammonium ion （from 0.01 mM to 10 mM） inhibit acetylene reduction and H₂-production to various degrees. The acetylene reduction and H₂-production were severely inhibited by 10mM ammonium.5. DCMU is an inhibitor of photosystem Ⅱ. It is well known that DCMU inhibits the O₂ evolution by blue-green algae. There is much controversy among different authors about the effects of DCMU on H₂-production by blue-green algae. We observed that the ethylene and hydrogen production was inhibited by about 20% by DCMU (2×10^-5).Both acetylene reduction and H₂-production were inhibited significantly by DNP, an uncoupler of photophosphorylation, at a concentration of 5×10^-4M.更多还原