Читать книгу Enzyme-Based Organic Synthesis - Cheanyeh Cheng - Страница 24

Enzymatic and microbial oxidations can be dated back to 2000 BCE with vinegar production that is based on the oxidation of ethanol by acetic acid bacteria. Enzymes involved in the biocatalyzed oxidations are dehydrogenases and oxidases. The more common coenzymes associated with dehydrogenases are nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide hydrogen (NAD⁺/NADH), nicotinamide adenine dinucleotide phosphate/nicotinamide adenine dinucleotide phosphate hydrogen (NADP⁺/NADPH), and flavin adenine dinucleotide/flavin adenine dinucleotide hydrogen (FAD/FADH₂), whereas oxidases are usually assisted by flavoproteins for transferring electrons to molecular oxygen. Dehydrogenases can be found in aerobic and anaerobic organisms or microorganisms; however, oxidases are not present in strictly anaerobic species. Nowadays, dehydrogenases and oxidases have been extensively used for selective oxidations and as an alternative synthetic strategy for conventional oxidations with the advantages of being environmentally friendly and highly chemo‐, regio‐, and stereoselective. Nevertheless, due to poor stability of the two enzymes at high substrate/product/organic solvent concentration and temperature, large‐scale bio‐oxidation processes were few. The functional groups involved in those bio‐oxidations include hydroxyls of primary and secondary alcohols, carbonyls of aldehydes, saturated C–C bonds, C–N bond of amino acids, amines, nitroalkanes, and thiols [1].