“…The oxidation reaction of reduced enzyme-3HB, prepared either by NADH or dithionite reduction, showed similar kinetics. For Class B flavoprotein monooxygenases such as phenylacetone monooxygenase (31), cyclohexanone monooxgenase (32), and L-ornithine monooxygenase (33)(34)(35), the binding of NAD(P) ϩ is required to stabilize the C4a-peroxyflavin intermediate (36,37). For Class C enzymes such as bacterial luciferase (38,39) and Class D enzymes such as the oxygenase component of p-hydroxyphenylacetate hydroxylase (27,40), C4a-hydroperoxyflavin can be detected in the absence of any bound ligand.…”