Hashimoto H, Misono H, Nagata S, Nagasaki S
Department of Agricultural Chemistry, Kochi University, Nankoku.
J Biochem. 1989 Jul;106(1):76-80. doi: 10.1093/oxfordjournals.jbchem.a122823.
The activation of lysine epsilon-dehydrogenase [EC 1.4.1.] by L-lysine was dependent on lysine concentration and was accompanied by association of the dimeric enzymes to a tetramer. The lysine concentration required for the half-maximal activation was 0.28 mM, which was lower than the Km value for L-lysine. In addition to L-lysine, several compounds, which were neither substrates nor inhibitors, activated the enzyme. The compounds which activated the enzyme have common structural characteristics: they have both a carboxyl group and a hydrophobic side chain. These activators also induced the association of the enzyme. The activation of the enzyme occurred well over the pH range 5.0 to 7.5, and the maximal activation was obtained by preincubation for 5 min at 30 degrees C and pH 7.4, when 5 mM L-lysine or 6-aminocaproate was used as an activator. NADH binding experiments indicated that about 2 mol of NADH bind to 1 mol of the tetrameric enzyme: the dimeric enzyme has one catalytic site. Binding experiments with n-[1-14C]heptanoate and L-[U-14C]lysine showed that approximately 2 mol of ligands bind to 1 mol of the dimeric enzyme and L-lysine could not bind to the catalytic site of the enzyme in the absence of NAD+. These results indicate the presence of one catalytic site and two activator binding binding sites in the dimeric enzyme.
赖氨酸ε-脱氢酶[EC 1.4.1.]被L-赖氨酸激活依赖于赖氨酸浓度，并且伴随着二聚体酶缔合形成四聚体。激活达到最大激活一半时所需的赖氨酸浓度为0.28 mM，该浓度低于L-赖氨酸的Km值。除L-赖氨酸外，几种既不是底物也不是抑制剂的化合物也能激活该酶。能激活该酶的化合物具有共同的结构特征：它们都有一个羧基和一个疏水侧链。这些激活剂也能诱导该酶的缔合。该酶在pH 5.0至7.5的范围内均能被很好地激活，当使用5 mM L-赖氨酸或6-氨基己酸作为激活剂时，在30℃和pH 7.4下预孵育5分钟可获得最大激活效果。NADH结合实验表明，约2摩尔NADH与1摩尔四聚体酶结合：二聚体酶有一个催化位点。用n-[1-14C]庚酸和L-[U-14C]赖氨酸进行的结合实验表明，约2摩尔配体与1摩尔二聚体酶结合，并且在没有NAD+的情况下，L-赖氨酸不能与该酶的催化位点结合。这些结果表明二聚体酶中存在一个催化位点和两个激活剂结合位点。
