d-Amino acid oxidase (DAO) has been suggested to be associated with the central nervous system diseases, such as schizophrenia. We newly synthesized a nonfluorescent 5-methylthio-d-kynurenine (MeS-d-KYN), which was converted to blue-fluorescent 6-MeS-kynurenic acid (MeS-KYNA, λex = 364 nm, λem = 450 nm) through a one-step reaction by incubation with DAO. It was revealed that fluorescence intensity increased accompanied by commercial porcine kidney DAO activity (unit) with a good correlation (R2 = 0.9972), suggesting that the fluorometric evaluation of DAO activity using MeS-d-KYN is feasible. MeS-d-KYN was applied to fluorescent DAO imaging in cultured LLC-PK1 cells, and the blue fluorescence of MeS-KYNA overlapped considerably with the location of peroxisomes, which was suggested to be the location of DAO in the cells. Because fluorescence was diminished in the presence of 6-chloro-1,2-benzisoxazol-3(2H)-one (CBIO), a DAO inhibitor, it was considered that DAO activity in cells could be directly evaluated using MeS-d-KYN as the substrate.
d-
氨基氧化酶(
DAO)被认为与精神分裂症等中枢神经系统疾病有关。我们新合成了非荧光5-甲基
硫代-d-
喹啉(MeS-d-KYN),通过与
DAO孵育一步反应,将其转化为蓝色荧光6-甲基
硫代-
喹啉酸(MeS-KYNA,λex = 364 nm,λem = 450 nm)。结果表明,荧光强度随商业猪肾
DAO活性(单位)的增加而增加,相关性良好(R2 = 0.9972),表明使用MeS-d-KYN对
DAO活性进行荧光测定是可行的。MeS-d-KYN被用于培养的LLC-PK1细胞中
DAO的
荧光成像,MeS-KYNA的蓝色荧光与
过氧化物酶体的位置高度重叠,这表明
过氧化物酶体是细胞中
DAO的所在地。由于在
DAO
抑制剂6-
氯-1,2-苯并
异恶唑-3(2H)-酮(CBIO)存在下荧光减弱,因此认为可以使用MeS-d-KYN作为底物直接评估细胞中的
DAO活性。