Houchins J P, Burris R H
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706.
Plant Physiol. 1981 Sep;68(3):712-6. doi: 10.1104/pp.68.3.712.
Reactions of the uptake hydrogenase from Anabaena 7120 (A.T.C.C. 27893, Nostoc muscorum) were examined in whole filaments, isolated heterocysts, and membrane particles. Whole filaments or isolated heterocysts that contained nitrogenase consumed H(2) in the presence of C(2)H(2) or N(2) in a light-dependent reaction. If nitrogenase was inactivated by O(2) shock, filaments catalyzed H(2) uptake to an unidentified endogenous acceptor in the light. Addition of NO(3) (-) or NO(2) (-) enhanced these rates. Isolated heterocysts consumed H(2) in the dark in the presence of electron acceptors with positive midpoint potentials, and these reactions were not enhanced by light. With acceptors of negative midpoint potential, significant light enhancement of H(2) uptake occurred. Maximum rates of light-dependent uptake were approximately 25% of the maximum dark rates observed. Membrane particles prepared from isolated heterocysts showed similar specificity for electron acceptors. These particles catalyzed a cyanide-sensitive oxyhydrogen reaction that was inactivated by O(2) at O(2) concentrations above 2%. Light-dependent H(2) uptake to low potential acceptors by these particles was inhibited by dibromothymoquinone but was insensitive to cyanide. In the presence of O(2), light-dependent H(2) uptake occurred simultaneously with the oxyhydrogen reaction. The pH optima for both types of H(2) uptake were near 7.0. These results further clarify the role of uptake hydrogenase in donating electrons to both the photosynthetic and respiratory electron transport chains of Anabaena.
对鱼腥藻7120（美国模式培养物集存库27893，地木耳念珠藻）摄取氢化酶的反应，在完整丝状体、分离的异形胞和膜颗粒中进行了研究。含有固氮酶的完整丝状体或分离的异形胞在光照反应中，在有乙炔或氮气存在的情况下消耗氢气。如果固氮酶因氧气冲击而失活，丝状体在光照下催化氢气摄取到一种未知的内源性受体。添加硝酸根离子或亚硝酸根离子可提高这些速率。分离的异形胞在有正中点电位的电子受体存在下于黑暗中消耗氢气，且这些反应不受光照增强。对于负中点电位的受体，氢气摄取有显著的光照增强。光照依赖性摄取的最大速率约为观察到的最大黑暗速率的25%。从分离的异形胞制备的膜颗粒对电子受体表现出相似的特异性。这些颗粒催化一种对氰化物敏感的氢氧反应，该反应在氧气浓度高于2%时被氧气灭活。这些颗粒对低电位受体的光照依赖性氢气摄取受到二溴百里香醌的抑制，但对氰化物不敏感。在有氧气存在的情况下，光照依赖性氢气摄取与氢氧反应同时发生。两种类型的氢气摄取的最适pH值都接近7.0。这些结果进一步阐明了摄取氢化酶在向鱼腥藻的光合和呼吸电子传递链提供电子中的作用。
