Department of Molecular Microbiology and Biotechnology, Institute of Biochemistry, Life Sciences Center, Vilnius University, Saulėtekio av., 10257 Vilnius, Lithuania.
Department of Protein-DNA Interactions, Institute of Biotechnology, Life Sciences Center, Vilnius University, Saulėtekio av. 7, 10257 Vilnius, Lithuania.
Sci Adv. 2023 Feb 3;9(5):eade4361. doi: 10.1126/sciadv.ade4361.
Cytidine deaminases (CDAs) catalyze the hydrolytic deamination of cytidine and 2'-deoxycytidine to uridine and 2'-deoxyuridine. Here, we report that prokaryotic homo-tetrameric CDAs catalyze the nucleophilic substitution at the fourth position of -acyl-cytidines, -alkyl-cytidines, and -alkyloxycarbonyl-cytidines, and -alkylthio-uridines and -alkyl-uridines, converting them to uridine and corresponding amide, amine, carbamate, thiol, or alcohol as leaving groups. The x-ray structure of a metagenomic CDA_F14 and the molecular modeling of the CDAs used in this study show a relationship between the bulkiness of a leaving group and the volume of the binding pocket, which is partly determined by the flexible β3α3 loop of CDAs. We propose that CDAs that are active toward a wide range of substrates participate in salvage and/or catabolism of variously modified pyrimidine nucleosides. This identified promiscuity of CDAs expands the knowledge about the cellular turnover of cytidine derivatives, including the pharmacokinetics of pyrimidine-based prodrugs.
胞苷脱氨酶（CDAs）催化胞苷和 2'-脱氧胞苷的水解脱氨反应，生成尿苷和 2'-脱氧尿苷。在这里，我们报告了原核同型四聚体 CDAs 能够催化 -酰基胞苷、-烷基胞苷和 -烷氧基羰基胞苷以及 -烷基硫代尿苷和 -烷基尿苷的第四位亲核取代反应，将它们转化为尿苷和相应的酰胺、胺、氨基甲酸酯、硫醇或醇作为离去基团。通过对一个宏基因组 CDA_F14 的 X 射线结构和本研究中使用的 CDAs 的分子建模，我们发现离去基团的体积与结合口袋的体积之间存在关系，这部分是由 CDAs 的柔性β3α3 环决定的。我们提出，对广泛的底物具有活性的 CDAs 参与各种修饰的嘧啶核苷的补救和/或分解代谢。这种 CDAs 的混杂活性扩展了关于胞苷衍生物细胞周转率的知识，包括嘧啶类前药的药代动力学。
