Department of Food Science and Technology, University of California, Davis, California 95616.
Plant Physiol. 1978 Nov;62(5):798-801. doi: 10.1104/pp.62.5.798.
5-Oxoprolinase has been found to be widely distributed in higher plants. This enzyme catalyzes the ATP-dependent hydrolysis of 5-oxo-l-proline (l-pyrollidone carboxylate, l-pyroglutamate) to glutamate. The enzyme has been purified almost 60 fold from wheat germ (Triticum aestivum L). This enzyme requires a divalent cation, either Mn(2+) or Mg(2+), and a combination of both appears to be the most effective. There is also an absolute requirement for a monovalent cation best fulfilled by either NH(4) (+) or K(+). The K(m) for ATP is 0.4 mm and for 5-oxo-l-proline is 14 mum. A small amount of activity is observed when other purine nucleotides such as ITP and GTP replace ATP. The substitution of the pyrimidine nucleotides CTP and UTP for ATP yield almost completely inactive preparations. The enzyme appears to have an active sulfhydryl group since there is an increase in activity in the presence of dithioerythritol. Preincubation with reagents such as N-ethylmaleimide or iodoacetamide lead to complete inactivation. The presence of this enzyme leads to the speculation of the possible presence of a gamma-glutamyl cycle in higher plants.
5-氧脯氨酸酶广泛存在于高等植物中。这种酶能催化 ATP 依赖的 5-氧脯氨酸（l-吡咯烷酮羧酸，l-焦谷氨酸）水解生成谷氨酸。该酶已从麦胚（小麦）中得到近 60 倍的纯化。这种酶需要一种二价阳离子，Mn(2+)或 Mg(2+)，两者的组合似乎是最有效的。它还绝对需要一种单价阳离子，最好是 NH(4) (+)或 K(+)。ATP 的 K(m)值为 0.4mm，5-氧脯氨酸的 K(m)值为 14 mum。当其他嘌呤核苷酸如 ITP 和 GTP 替代 ATP 时，会观察到少量的活性。嘧啶核苷酸 CTP 和 UTP 的替代几乎会产生完全无活性的制剂。该酶似乎具有活性巯基基团，因为在存在二硫苏糖醇的情况下，酶的活性增加。与 N-乙基马来酰亚胺或碘乙酰胺等试剂预孵育会导致完全失活。这种酶的存在使得人们推测高等植物中可能存在γ-谷氨酰循环。
