1.14.13.172 metabolism binding of salicylate and O2 is fast. Transfer of the Rieske electron required to form the gentisate product occurs through bonds over about 12 A and must also be very fast. The observed rate constant for this reaction is much slower than expected and sensitive to substrate type. A transient intermediate (lambdamax of 700 nm) with an EPR resonance at g 4.3 is observed after product is formed in the active site. Gentisate binds to the mononuclear iron via its C5-OH in the intermediate. Rereduction of the metal centers accelerates product release about 300fold 764170 1.14.13.172 physiological function enzyme S5H hydroxylates salicylate into gentisate and is involved in the degradation of aromatic compounds. SalD is an essential component of the S5H complex 743932