Light‐Activated Electron Transfer and Catalytic Mechanism of Carnitine Oxidation by Rieske‐Type Oxygenase from Human Microbiota

Abstract

Oxidation of quaternary ammonium substrate, carnitine by non‐heme iron containing Acinetobacter baumannii (Ab) oxygenase CntA/reductase CntB is implicated in the onset of human cardiovascular disease. Herein, we develop a blue‐light (365 nm) activation of NADH coupled to electron paramagnetic resonance (EPR) measurements to study electron transfer from the excited state of NADH to the oxidized, Rieske‐type, [2Fe‐2S]2+ cluster in the AbCntA oxygenase domain with and without the substrate, carnitine. Further electron transfer from one‐electron reduced, Rieske‐type [2Fe‐2S]1+ center in AbCntA‐WT to the mono‐nuclear, non‐heme iron center through the bridging glutamate E205 and subsequent catalysis occurs only in the presence of carnitine. The electron transfer process in the AbCntA‐E205A mutant is severely affected, which likely accounts for the significant loss of catalytic activity in the AbCntA‐E205A mutant. The NADH photo‐activation coupled with EPR is broadly applicable to trap reactive intermediates at low temperature and creates a new method to characterize elusive intermediates in multiple redox‐centre containing proteins.

Living intracellular inorganic-microorganism biohybrid system for efficient solar hydrogen generation

“…Finally, the photoelectrochemical responses of E. coli were evaluated and are presented in Figure 1F. The electrode substrate did not present any light response, and then, after it bounded the living E. coli on the surface of the electrode, an obvious photocurrent response can be observed, which suggests the intrinsic photo-responsive activity of living E. coli due to the light-induced electron transfer from the excited NADH to oxidized NAD + , 15 and then, after the addition of glucose, the photocurrent response was further enhanced and verified the photo-induced glucose reforming.…”

Contrasting Mechanisms of Aromatic and Aryl-Methyl Substituent Hydroxylation by the Rieske Monooxygenase Salicylate 5-Hydroxylase

“…Rieske oxygenases (ROs) are nonheme iron-containing enzymes that catalyze a remarkably expansive range of reactions and act upon a diverse group of substrate chemical types. − Found widely across nature, − the ROs are increasingly appreciated for their roles and applications in human health, ,− environmental biotechnology, − agriculture, and chemoenzymatic synthesis. − Collectively, the catalytic repertoire of the RO family exceeds even those of other well-studied oxygenases, including cytochrome P450, dinuclear iron-containing hydrocarbon monooxygenases, flavin oxygenases, and α-ketoacid-linked monooxygenases. ,− …”