Dolfing J
DLO Research Institute for Agrobiology and Soil Fertility, Haren, The Netherlands.
FEMS Microbiol Lett. 1998 Oct 15;167(2):271-4. doi: 10.1111/j.1574-6968.1998.tb13238.x.
Biological halogenation of aromatic compounds implies the generation of reducing equivalents in the form of e.g. NADH. Thermodynamic calculations show that coupling the halogenation step to a step in which the reducing equivalents are oxidized with a potent oxidant such as O2 or N2O makes the halogenation reaction thermodynamically feasible without the input of additional energy in the form of e.g. NADH. In a current model on the halogenation of tryptophan to 7-chloro-L-tryptophan NADH and O2 are proposed as co-substrates in a reaction in which the aromatic compound is oxidized via an epoxide as intermediate. The thermodynamic calculations thus indicate that such a route hinges on mechanistic insights but has no thermodynamic necessity. Furthermore the calculations suggest that halogenation of tryptophan and other aromatic compounds should be possible with N2O, and possibly even with nitrate replacing O2 as the oxidant.
芳香族化合物的生物卤化意味着以例如NADH的形式产生还原当量。热力学计算表明，将卤化步骤与还原当量被强氧化剂（如O2或N2O）氧化的步骤相耦合，使得卤化反应在热力学上可行，而无需以例如NADH的形式输入额外能量。在当前关于色氨酸卤化为7-氯-L-色氨酸的模型中，NADH和O2被提议作为反应中的共底物，其中芳香族化合物通过环氧化物作为中间体被氧化。因此，热力学计算表明，这样一条途径取决于机理见解，但没有热力学必要性。此外，计算表明，用N2O，甚至可能用硝酸盐代替O2作为氧化剂，色氨酸和其他芳香族化合物的卤化应该是可能的。
