Identifying and modeling sources of reducing equivalents in the nitric oxide detoxification response of Escherichia coli

Abstract

The important role of nitric oxide (NO) as a key mediator of macrophage cytotoxicity makes a comprehensive understanding of its metabolism in bacteria a valuable tool for investigating both bacterial pathogenesis and the workings of the immune system. The large set of reactions involving NO and other reactive nitrogen species (RNS) as intermediates form a complex network, the kinetic properties of which have been shown to be critical to understanding the distribution of NO within the bacterial cell as well as identifying the primary cellular pathways responsible for NO detoxification and repair of NO-damaged cellular components. In this thesis, we begin the expansion of an existing kinetic model for NO metabolism in Escherichia coli to incorporate the reactions of central metabolism. The respective roles of glycolysis and the pentose phosphate pathway in supplying the reducing equivalents necessary for NO detoxification and damage repair during NO stress appear to be distinct from one another, with glycolysis showing the greater capacity for NAD(P)H production. While our extended model is still unsuitable for making quantitative predictions, it shows good qualitative agreement with experimental data and represents a significant conceptual improvement over previous models in that concentrations of NAD(P)H and NAD(P)\(^{+}\) are fully simulated by the model equations instead of being fixed or defined empirically by analytic functions.