Misono H, Hashimoto H, Uehigashi H, Nagata S, Nagasaki S
Department of Agricultural Chemistry, Kochi University.
J Biochem. 1989 Jun;105(6):1002-8. doi: 10.1093/oxfordjournals.jbchem.a122757.
Lysine epsilon-dehydrogenase, which has been purified to homogeneity from the extract of Agrobacterium tumefaciens ICR 1600, had a molecular weight of approximately 78,000 and consisted of two subunits identical in molecular weight (about 39,000). The enzyme showed a high substrate specificity. In addition to L-lysine, S-(beta-aminoethyl)-L-cysteine was deaminated by the enzyme, but to a far lesser extent. NAD+ and some NAD+ analogs (deamino-NAD+ and 3-acetylpyridine-NAD+) served as a cofactor. The pH optimum was at about 9.7 for the deamination of L-lysine. Although the NAD+ saturation curve was hyperbolic, a sigmoid saturation curve for L-lysine was obtained with the diluted enzyme solution, in which the dimeric enzyme was predominant. The reversible association of the enzyme to the tetramer was induced either by increasing the enzyme concentration or by addition of L-lysine. The preincubation of the enzyme with 5 mM L-lysine resulted in a 2-fold increase in the activity and gave a hyperbolic saturation curve for L-lysine. Upon modification of SH groups of the enzyme with DTNB, neither the interconversion between the dimer and the tetramer nor the activation by L-lysine occurred. These results indicated that the dimeric enzyme was activated by L-lysine and the activation resulted from the association of two dimeric enzymes to form a tetramer.
赖氨酸ε-脱氢酶已从根癌土壤杆菌ICR 1600的提取物中纯化至同质，其分子量约为78,000，由两个分子量相同（约39,000）的亚基组成。该酶表现出高底物特异性。除L-赖氨酸外，该酶还能使S-（β-氨基乙基）-L-半胱氨酸脱氨，但程度要小得多。NAD +和一些NAD +类似物（脱氨基-NAD +和3-乙酰吡啶-NAD +）作为辅因子。L-赖氨酸脱氨的最适pH约为9.7。尽管NAD +饱和曲线是双曲线型的，但用稀释的酶溶液（其中二聚体酶占主导）获得了L-赖氨酸的S形饱和曲线。通过增加酶浓度或添加L-赖氨酸可诱导酶与四聚体的可逆缔合。用5 mM L-赖氨酸对酶进行预孵育导致活性增加2倍，并给出了L-赖氨酸的双曲线饱和曲线。用DTNB修饰酶的SH基团后，二聚体与四聚体之间的相互转化以及L-赖氨酸的激活均未发生。这些结果表明二聚体酶被L-赖氨酸激活，并且激活是由两个二聚体酶缔合形成四聚体所致。
