Inactivation leads to covalent attachment of 2 equiv of inactivator after gel filtration; upon urea denaturation, 1 equiv of radioactivity remains bound to the enzyme. This suggests that, unlike the open-chain anlogue, the conformationally rigid analogue becomes, at least partially, attached to an active-site residue. It appears that the conformational constraint has a larger effect on inactivators that
最近,我们发现(Qiu,J .; Pingsterhaus,JM; Silverman,RBJ Med。Chem。1999,42,4725-4728),
GABA氨基转移酶(
GABA-AT)灭活剂vi
GABAtrin的构象刚性类似物不是
GABA-灭活剂。在。为了确定这是否是
GABA-AT灭活剂的普遍现象,合成了其他
GABA-AT灭活剂的几种单和二卤素取代的构象刚性类似物(7-15),即4-
氨基-5-卤代
戊酸。潜在的
GABA-AT灭活剂。其中四个(+)-7,(-)-9,(+)-10和(+)-15是灭活剂,尽管不如相应的开链类似物有效。
氟和
溴取代的类似物的最大失活速率常数k(inact)是可比的,表明CX键的断裂不是决定速率的。与该观察结果一致的发现是,[3-(2)H] -10对3.3的失活表现出
氘同位素效应,这表明CH键的裂解是决定速率的步骤。
氟化类似物7灭活
GABA-AT的速率是相应的开链类