烟酸、烟酰胺和大豆根瘤中豆血红蛋白的反应性。
Nicotinate, nicotinamide, and the reactivity of leghemoglobin in soybean root nodules.
机构信息
Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0718.
出版信息
Plant Physiol. 1991 Feb;95(2):551-5. doi: 10.1104/pp.95.2.551.
Nicotinate has been postulated to interfere with the binding of O(2) to ferrous leghemoglobin in soybean (Glycine max) root nodules. For such a function, the levels of nicotinate in nodules must be sufficiently high to bind a significant amount of leghemoglobin. We have measured levels of nicotinate, nicotinamide, and leghemoglobin in soybean nodules from plants 34 to 73 days after planting in a glasshouse. On a per gram nodule fresh weight basis, levels between 10.4 and 21 nanomoles for nicotinate, 19.2 and 37.8 nanomoles for nicotinamide, and 170 to 280 nanomoles for leghemoglobin were measured. Even if all the nicotinate were bound to ferrous leghemoglobin, only 11% or less of the total leghemoglobin would be unavailable for binding O(2). Using the measured levels of nicotinate and a pH of 6.8 in the cytosol of presenescent soybean nodules, we estimate that the proportion of ferrous leghemoglobin bound to nicotinate in such nodules would be less than 1%. These levels of nicotinate are too low to interfere with the reaction between ferrous leghemoglobin and O(2) in soybean root nodules.
烟酸被假设会干扰氧（O(2)）与大豆（Glycine max）根瘤中铁氧还蛋白的结合。对于这样的功能，豆瘤中烟酸的水平必须足够高，才能结合大量的铁氧还蛋白。我们已经测量了在温室中种植 34 至 73 天后大豆根瘤中的烟酸、烟酰胺和铁氧还蛋白的水平。以每克新鲜豆瘤为基础，测量到的烟酸水平在 10.4 到 21 纳摩尔之间，烟酰胺水平在 19.2 到 37.8 纳摩尔之间，铁氧还蛋白水平在 170 到 280 纳摩尔之间。即使所有的烟酸都与亚铁氧还蛋白结合，也只有 11%或更少的总铁氧还蛋白无法与氧（O(2)）结合。根据测量到的烟酸水平和预衰老大豆豆瘤胞质溶胶的 pH 值 6.8，我们估计在这种豆瘤中，与烟酸结合的亚铁氧还蛋白比例将小于 1%。这些烟酸水平太低，不会干扰大豆根瘤中铁氧还蛋白与氧（O(2)）之间的反应。
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