Kinetic characteristics of L-lysine α- oxidase from Trichoderma cf. aureoviride Rifai VKM F-4268D: Substrate specificity and allosteric effects

Abstract The present work aims to investigate the kinetic characteristics of homodimer enzyme L -lysine α-oxidase from Trichoderma cf. aureoviride Rifai VKM F-4268D, taking into account allosteric effects. The enzyme was first shown to reveal positive cooperativeness, h =2.05±0.15. Using additional opportunities of Hill coefficient the value of the Michaelis–Menten constant has been estimated, K m =1.015∙10 −5 М, indicating high strength of substrate binding to the active site of each subunit. High selectivity and absolute L -stereospecificity of the enzyme were shown. The inhibition of L -lysine conversion by non-cleavable lysine analogs as well as the reaction product was found out to take place. These effects have been evaluated only as the inhibition coefficients ( %). A more detailed study of these inhibition effects was complicated because of the cooperativeness of enzyme subunits mentioned above. The kinetic scheme of L -lysine α-oxidase was proposed involving parallel-subsequent action of each of two subunits in the catalytic act. We think that the results obtained will be useful for studying the kinetic properties of other multi-subunit enzymes and improve understanding of the mechanisms of their action.