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

•Positive cooperativity of subunits in L-lysine α-oxidase was first shown.•The kinetic scheme of L-lysine deamination involving parallel-subsequent action of each subunit in the catalytic act was proposed.•The Michaelis-Menten constant has been estimated using the Hill coefficient and the equation developed for allosteric enzymes.•High selectivity and absolute L-stereospecificity of the enzyme were found.•L-Lysine conversion is inhibited by non-cleavable analogs of lysine as well as by the reaction product.

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, Km=1.015∙10−5М, 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.

Graphical abstractDownload high-res image (88KB)Download full-size image