基于BODIPY母核的羧酸酯酶1特异性荧光探针底物的设计研发

Design and development of fluorescent probe substrates for carboxylesterase 1 using BODIPY as the basic fluorophore

羧酸酯酶1(carboxylesterase 1,CE1)是哺乳动物体内分布的一种重要的丝氨酸水解酶,广泛参与多种内外源性酯类化合物(包括胆固醇酯等内源物,以及酯类药物及杀虫剂等外源物)的水解代谢。本研究基于人羧酸酯酶1(hCE1)偏好底物的结构特征,选取8-羧酸-BODIPY为荧光母核,设计合成了4种BODIPY-8-羧酸酯衍生物,进而通过单酶筛选和酶抑制实验考察了hCE1催化4种酯类底物的特异性。研究发现,BODIPY-8-羧酸酯的醇基部分越小,hCE1对底物的选择性越高,BODIPY-8-羧酸甲酯(BCM)和BODIPY-8-羧酸乙酯(BCE)均可以作为hCE1的特异性荧光探针底物。在此基础上,选择了水解速率更快的BCM为hCE1探针底物,进一步考察了BCM在人肝微粒体(HLM)和hCE1单酶中的水解动力学,并借助该底物开展了hCE1抑制剂的高效表征研究。研究发现BCM在HLM和hCE1中的酶动力学行为及K_m值非常接近,表明hCE1是HLM中参与BCM水解的主要代谢酶。此外,抑制剂表征实验表明BCM可用于hCE1抑制剂的高效筛选与评价,且可用HLM代替hCE1单酶进行酶抑制剂的筛选与评价。

Carboxylesterase 1 （CE1） is an important serine hydrolase in mammals, which involved in the hydrolysis of a variety of compounds （endogenous substrates like cholesterol and xenobiotic compounds like ester-contain drugs and pesticides）. This study aimed to design and develop the fluorescent probe substrates for human carboxylesterase 1 （hCE 1）, on the basis of the structural features of hCE 1 preferred substrates. Four carboxylic esters deriving from BODIPY-8-carboxylic acid were designed and synthesized. After then, reaction phenotyping assays and chemical inhibition assays were used to evaluate the selectivity of these four ester derivatives towards hCE1. Our results clearly demonstrated that the substrate specificity of these ester substrates towards hCE1 would be improved with the decrease of the alcohol group on BODIPY-8-carboxylesters, while BODIPY-8-carboxylesters with small alcohol groups including methyl （BCM） and ethyl （BCE） esters could serve as the ideal probe substrates for hCE 1. Given that BCM exhibit rapid hydrolytic rate in hCE 1, we further investigate the enzymatic kinetics of this fluorescent probe substrate in both human liver microsomes （HLM） and recombinant hCE1, as well as to explore its potential application in high-throughput screening of hCE1 inhibitors by using HLM as enzyme source. The results showed that the kinetic behaviors and the affinity of BCM in HLM is much closed to those in recombinant hCE 1, implying that hCE 1 played the key roles in BCM hydrolysis in HLM. Furthermore, the inhibition study demonstrated that BCM could be used for rapid screening and characterization ofhCE1 inhibitors, by using HLM to replace recombinant hCE1 as enzyme source.