Lindström P
Biochim Biophys Acta. 1986 Nov 19;884(2):276-81. doi: 10.1016/0304-4165(86)90174-1.
Aromatic-L-amino-acid decarboxylase activity has been measured in intact or homogenised pancreatic islets of ob/ob mice (Umeå ob/ob). The method used involves the trapping and measuring of the 14CO2 released from L-[1-14C]dihydroxyphenylalanine (L-dopa). Islets showed a decarboxylase activity which was dependent on pyridoxal phosphate and inhibitable by 0.1 mM benserazide or 0.1 mM alpha-monofluoromethyldopa. Maximum activity in intact islets was about 330 mmol/kg dry islet per h with an apparent Km of 3.3 mM. Islet homogenates had a Vmax of about 120 mmol/kg per h with a Km of 0.3 mM. L-5-Hydroxytryptophan, m-tyrosine and o-tyrosine interfered with the decarboxylation of L-dopa in a way that suggested a high activity also towards those substrates. L-Phenylalanine, L-tyrosine and D-glucose had no effect. At 0.05 mM L-dopa islet homogenates showed a much higher activity than homogenates of liver, kidney, or spleen. Islet uptake of L-[3H]dopa was well in excess of the decarboxylation rate and thus probably not rate-limiting. It is concluded that mouse pancreatic islets have a high activity of aromatic-L-amino-acid decarboxylase. This is in accordance with previous suggestions of a stimulatory effect of this enzyme on insulin secretion.
已对ob/ob小鼠（于默奥ob/ob）完整或匀浆的胰岛中的芳香族L-氨基酸脱羧酶活性进行了测定。所采用的方法涉及捕获并测量从L-[1-¹⁴C]二羟基苯丙氨酸（L-多巴）释放的¹⁴CO₂。胰岛显示出一种依赖于磷酸吡哆醛的脱羧酶活性，且可被0.1 mM苄丝肼或0.1 mMα-单氟甲基多巴抑制。完整胰岛中的最大活性约为每小时330 mmol/kg干胰岛，表观Km为3.3 mM。胰岛匀浆的Vmax约为每小时120 mmol/kg，Km为0.3 mM。L-5-羟色氨酸、间酪氨酸和邻酪氨酸以一种表明对这些底物也具有高活性的方式干扰L-多巴的脱羧作用。L-苯丙氨酸、L-酪氨酸和D-葡萄糖没有影响。在0.05 mM L-多巴时，胰岛匀浆显示出比肝脏、肾脏或脾脏匀浆高得多的活性。胰岛对L-[³H]多巴的摄取远远超过脱羧速率，因此可能不是限速因素。结论是小鼠胰岛具有高活性的芳香族L-氨基酸脱羧酶。这与先前关于该酶对胰岛素分泌有刺激作用的推测一致。
