cysteine-tryptophylquinone and allysine

LodA is a novel lysine-ε-oxidase which possesses a cysteine tryptophylquinone cofactor. It is the first tryptophylquinone enzyme known to function as an oxidase. A steady-state kinetic analysis shows that LodA obeys a ping-pong kinetic mechanism with values of kcat of 0.22±0.04 s(-1), Klysine of 3.2±0.5 μM and KO2 of 37.2±6.1 μM. The kcat exhibited a pH optimum at 7.5 while kcat/Klysine peaked at 7.0 and remained constant to pH 8.5. Alternative electron acceptors could not effectively substitute for O2 in the reaction. A mechanism for the reductive half reaction of LodA is proposed that is consistent with the ping-pong kinetics.

Topics: 2-Aminoadipic Acid; Bacterial Proteins; Coenzymes; Dipeptides; Hydrogen-Ion Concentration; Indolequinones; Kinetics; Lysine; Marinomonas; Models, Chemical; Proteins