The Hydroxylamine Oxidizing System of Nitrosomonas

胡珀9316906在土壤中，化肥氨氧化为亚硝酸盐(NH_3+1.502-HNO_2+H_2)，由化学自养硝化细菌欧洲亚硝酸单胞菌。亚硝酸盐被硝酸杆菌氧化成硝酸盐，这是非豆类作物中N的主要来源。大多数食物氮的巨大经济转化是由亚硝化单胞菌进行的。在土壤中，亚硝化单胞菌在NH3氧化过程中或反硝化细菌还原硝酸盐过程中产生的氮气损失具有重要的经济意义。通过使用亚硝化单胞菌的氨氧化抑制剂来尝试通过反硝化来控制农业损失。这对提高对氨氧化反应机理的认识具有重要意义。NH3被O2氧化成NH_2OH，然后被羟胺氧化还原酶“HAO”氧化(NH_2OH+H20-HN02+4E-+4H+)。HOO是一种大而异常复杂的血红素蛋白(7个c-血红素和1个底物结合。“p460”组每63 kDa蛋白)。四个电子从HAO传递到四氢血红素细胞色素c-554。两个电子从细胞色素c-554以单独的电子转移链传递到氨氧化反应。另外两个电子传递到膜末端氧化酶、异化亚硝酸盐还原酶(在低氧条件下生长)、依赖于ATP的NAD还原酶或过氧化物酶(清除过氧化氢)。本项目的目标是对HAO酶进行分析。我们打算确定HAO的结构细节，并特别关注活跃的地点和成交机制。该方法包括光谱学、多肽分析、动力学、自杀底物、电子顺磁共振光谱、穆斯堡尔光谱和X射线结晶学分析。土壤和水体细菌亚硝化单胞菌对自然界中氮素的循环、温室气体和臭氧破坏气体的产生、农业中氮素的有效性和氯化污染物的降解都是至关重要的。这个项目涉及对生物催化剂结构的研究，使生物体能够发挥这些作用。该酶将一种含氮中间体羟胺氧化成亚硝酸盐。被称为羟胺氧化还原酶。我们打算完成酶的结构测定。然后，通过研究酶上基团的颜色变化和用化学方法测量中间化合物的生成，我们将找出它如何能够作为这种不寻常反应的催化剂。***

Hooper 9316906 In soils, fertilizer ammonia is oxidized to nitrite (NH3 + 1.5 02- HNO2 + H2) by the chemoautotrophic nitrifying bacterium Nitrosomonas europaea.. Nitrite is oxidized by Nitrobacter to nitrate, a primary source of N for food protein in non-leguminous crops. Of great economic transformation of most food nitrogen is carried out by Nitrosomonas. Of great economic importance is loss of N in soils as N-gases produced by Nitrosomonas during oxidation of NH3 or by reduction of nitrate by denitrifying bacteria. Control of agricultural loss by denitrification is attempted by the use of inhibitors of ammonia oxidation by Nitrosomonas. This gives significance to improved knowledge of the mechanism of oxidation of ammonia. NH3 is oxygenated by O2 to NH2OH which is then oxidized (NH2OH + H20- HN02 + 4e- + 4H+) by the enzyme hydroxylamine oxidoreductase "HAO". HAO is a large and unusually complex hemoprotein (7 c-hemes and 1 substrate binding. "P460" group per 63 kDa protein). Four electron pass from HAO to a tetraheme cytochrome c-554. Two electrons pass from cytochrome c-554 in a separate electron transfer chain to the ammonia oxidizing reaction. Two additional electrons pass to a membrane terminal oxidase, a dissimilatory nitrite reductase (during growth at low oxygen), to an ATP- dependent NAD reductase or a peroxidase (to scavange peroxide). The goal of this project is the analysis of the enzyme HAo. We intend to determine details of the structure of HAO with particular attention to the active site and mechanism of turnover. The approach involves optical spectroscopy, peptide analysis, kinetics, suicide substrates, electron paramagnetic resonance spectroscopy, Mossbauer spectroscopy and X-ray crystallographic analysis. %%% The soil and water bacterium, Nitrosomonas, is critical to the cycle of nitrogen in nature, to the production of a greenhouse and ozone destroying gas, to nitrogen availability in agriculture and in the degradation of chlori nated pollutants. This project is involved in the study of the structure of the biological catalyst which enables the organism to perform those roles. The enzyme oxidizes one of the nitrogenous intermediates, hydroxylamine, to nitrite. Is called hydroxylamine oxidoreductase. We intend to complete the determination of the structure of the enzyme. Then, by studying changes in the color of groups on the enzyme and by measuring the production of intermediate compounds by chemical means, we will find out how it is able to act as a catalyst for this unusual reaction. ***