Denner L A, Wu J Y
J Neurochem. 1985 Mar;44(3):957-65. doi: 10.1111/j.1471-4159.1985.tb12910.x.
There are two forms of glutamate decarboxylase (GAD) found in the rat brain. One form (form A) does not require exogenous pyridoxal-5'-phosphate (PLP) for activity whereas another form (form B) requires exogenous PLP for activity. These two forms differ greatly in temperature sensitivity, inactivation, and reactivation by the removal and readdition of PLP, electrophoretic mobility, and regional distribution. For instance, forms A and B are inactivated to an extent of 91% and 10%, respectively, by the treatment at 45 degrees C for 30 min; form A is greatly inactivated (77%) by the removal of PLP by aminooxyacetic acid and the readdition of PLP, whereas form B is only slightly inactivated (7%). Forms A and B can be clearly separated by 5% polyacrylamide gel electrophoresis in which form A migrates faster than form B. In all 10 brain regions studied, form A is present in smaller amounts than form B. This difference is greatest in the superior colliculus (the ratio of B to A is about 5), while in the locus coeruleus and cerebellum, forms A and B are present in nearly equal proportion. Forms A and B are similar with respect to relative abundance in hypotonic, isotonic, and hypertonic preparations, inhibition of catalytic activity by a carbonyl-trapping agent, immunochemical properties, and chromatographic patterns in a variety of systems. The significance of forms A and B and PLP in the regulation of gamma-amino-butyric acid (GABA) level is also discussed.
在大鼠脑中发现了两种形式的谷氨酸脱羧酶（GAD）。一种形式（A 型）的活性不需要外源性磷酸吡哆醛（PLP），而另一种形式（B 型）的活性需要外源性 PLP。这两种形式在温度敏感性、失活、通过去除和重新添加 PLP 进行的再激活、电泳迁移率和区域分布方面有很大差异。例如，在 45℃处理 30 30 分钟后，A 型和 B 型分别有 91%和 10%失活；用氨氧基乙酸去除 PLP 并重新添加 PLP 后，A 型大量失活（77%），而 B 型仅轻微失活（7%）。通过 5%聚丙烯酰胺凝胶电泳可以清楚地分离 A 型和 B 型，其中 A 型迁移速度比 B 型快。在所研究的所有 10 个脑区中，A 型的含量都比 B 型少。这种差异在上丘最大（B 型与 A 型的比例约为 5），而在蓝斑和小脑中，A 型和 B 型的比例几乎相等。A 型和 B 型在低渗、等渗和高渗制剂中的相对丰度、羰基捕获剂对催化活性的抑制、免疫化学性质以及在各种系统中的色谱模式方面相似。还讨论了 A 型和 B 型以及 PLP 在调节γ-氨基丁酸（GABA）水平中的意义。
