TY - JOUR AU - Bopp, Charlotte E. AU - Kohler, Hans-Peter E. AU - Hofstetter, Thomas B. PY - 2020/03/25 Y2 - 2024/03/28 TI - Enzyme Kinetics of Organic Contaminant Oxygenations JF - CHIMIA JA - Chimia VL - 74 IS - 3 SE - Scientific Articles DO - 10.2533/chimia.2020.108 UR - https://www.chimia.ch/chimia/article/view/2020_108 SP - 108 AB - <p>Enzymatic oxygenations initiate biodegradation processes of many organic soil and water contaminants. Even though many biochemical aspects of oxygenation reactions are well-known, quantifying rates of oxidative contaminant removal as well as the extent of oxygenation remains a major challenge. Because enzymes use different strategies to activate O<sub>2</sub>, reactions leading to substrate oxygenation are not necessarily limiting the rate of contaminant removal. Moreover, oxygenases react along unproductive pathways without substrate metabolism leading to O<sub>2</sub> uncoupling. Here, we identify the critical features of the catalytic cycles of selected oxygenases that determine rates and extents of biodegradation. We focus most specifically on Rieske dioxygenases, a subfamily of mononuclear non-heme ferrous iron oxygenases, because of their ability to hydroxylate unactivated aromatic structures and thus initiate the transformation of the most persistent organic contaminants. We illustrate that the rate-determining steps in their catalytic cycles range from O<sub>2</sub> activation to substrate hydroxylation, depending on the extent of O–O cleavage that is required for generating the reactive Fe-oxygen species. The extent of O<sub>2</sub> uncoupling, on the other hand, is highly substrate-specific and potentially modulated by adaptive responses to oxidative stress. Understanding the kinetic mechanisms of oxygenases will be key to assess organic contaminant biotransformation quantitatively.</p> ER -