植物病原菌,Agrobacterium tumefaciensのNAD^+依存性リジン脱水素酵素

概要

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Lysine dehydrogenase, which has been purified to homogeneity from A. tumefaciens, consisted of two identical subunits. The enzyme showed a high substrate specificity for L-lysine. The preincubation of the enzyme with L-lysine resulted in a 2-fold increase in the activity. The activation resulted from the association of two dimeric enzymes to form a tetramer. Upon modification of SH groups of the enzyme with 5, 5'-dithiobis (2-nitrobenzoate), neither the interconversion between the dimer and the tetramer nor the activation by L-lysine occurred. In addition to L-lysine, several compounds, which have both a carboxyl group and a hydrophobic side chain, activated the enzyme. The binding experiments showed that the presence of one catalytic site and two activator binding sites in the dimeric enzyme. In the enzyme reaction, the pro-R hydrogen at the prochiral C-6 carbon of L-lysine was specifically abstracted and transferred to the pro-R position at C-4 of the nicotinamide moiety of NAD^+. The enzyme could be used for the spectrophotometric assay of L-lysine.
日本ビタミン学会の論文
1991-01-25