Garber E A, Hollocher T C
J Biol Chem. 1982 May 10;257(9):4705-8.
During the concomitant reduction of [15N]nitrite and 14NO, the denitrifying bacterium Pseudomonas stutzeri produced considerable amounts of isotopically mixed N2O (14,15N2O) but did not isotopically intermix the nitrite and NO pools (Garber, E. A. E., and Hollocher, T. C. (1981) J. Biol. Chem. 256, 5459-5465). It was determined that the mass spectrometric abundance of 14N15NO was about equal to that of 15N14NO in 14,15N2O by examination of the abundances of 14NO+, 15NO+, and 15N2+ that arose from the fragmentation of N2O+ species in the mass spectrometer. This positional isotopic equivalence requires that N2O arose from [15N]nitrite and 14NO by a process in which loss of oxygen occurred with equal probability from 15N and 14N precursors and suggests that at some point the precursors were identical if monomeric or effectively symmetrical if dimeric. One pathway, which is consistent with the available data and for which there is chemical precedence, is the reduction of nitrite and NO to nitroxyl (NOH or HNO), dimerization of free nitroxyl to a dinitrogen intermediate of short half-life, and dehydration of this intermediate to form N2O.
在[15N]亚硝酸盐和14NO同时还原的过程中，反硝化细菌施氏假单胞菌产生了大量同位素混合的N2O（14,15N2O），但没有使亚硝酸盐和NO库发生同位素混合（加伯，E.A.E.，和霍洛彻，T.C.（1981年）《生物化学杂志》256卷，5459 - 5465页）。通过检测质谱仪中N2O + 物种碎片化产生的14NO + 、15NO + 和15N2 + 的丰度，确定了14,15N2O中14N15NO的质谱丰度与15N14NO的质谱丰度大致相等。这种位置同位素等效性要求N2O由[15N]亚硝酸盐和14NO通过一个过程产生，在这个过程中，15N和14N前体失去氧的概率相等，这表明如果前体是单体，则在某个点上它们是相同的；如果是二聚体，则是有效对称的。一条与现有数据一致且有化学先例的途径是，将亚硝酸盐和NO还原为硝酰基（NOH或HNO），游离硝酰基二聚化为半衰期较短的二氮中间体，以及该中间体脱水形成N2O。
