Kaur Gundeep, Horton John R, Tzertzinis George, Zhou Jujun, Schildkraut Ira, Cheng Xiaodong
Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
New England Biolabs, Ipswich, Massachusetts, USA.
J Biol Chem. 2025 Jun 10;301(7):110357. doi: 10.1016/j.jbc.2025.110357.
Helix pomatia AMP deaminase (HPAMPD), an enzyme enriched in the foot muscle of the mollusk H. pomatia, exhibits deaminase activity on adenosine-5'-monophosphate (AMP). HPAMPD is the first member of the adenosine deaminase-related growth factor (ADGF) family to prefer the nucleotide AMP over the nucleoside adenosine. To investigate the substrate selectivity of HPAMPD, we determined its structure in both the apo form and in complex with the adenosine analogs pentostatin and pentostatin-5'-monophosphate. Structurally, HPAMPD adopts a fold similar to human ADA2, an ADGF family member. HPAMPD has acquired the ability to interact with the 5'-monophosphate group of AMP through polar and charged residues located in three key structural elements: (1) the loop immediately following strand β1; (2) the loop between helices αH and αI; and (3) the end of strand β5 and its adjacent loop. We engineered a chimeric deaminase by integrating these elements from HPAMPD into another related mollusk nucleoside adenosine deaminase, Aplysia ADGF. The chimeric enzyme efficiently deaminates AMP, demonstrating a gained substrate specificity, while retaining the adenosine deamination activity of Aplysia ADGF. The phosphate-binding feature of HPAMPD is a hallmark of nucleotide deaminases, conserved among AMP and N6-methyl-AMP (6mAMP) deaminases. We discuss the human adenosine deaminases each with distinct substrate specificities for the nucleoside, the nucleotide (AMP), and its methylated form, 6mAMP.
罗马蜗牛AMP脱氨酶（HPAMPD）是一种在软体动物罗马蜗牛足部肌肉中富集的酶，对5'-单磷酸腺苷（AMP）具有脱氨酶活性。HPAMPD是腺苷脱氨酶相关生长因子（ADGF）家族中第一个更倾向于核苷酸AMP而非核苷腺苷的成员。为了研究HPAMPD的底物选择性，我们测定了其无配体形式以及与腺苷类似物喷司他丁和喷司他丁-5'-单磷酸形成复合物时的结构。在结构上，HPAMPD采用了与ADGF家族成员人类ADA2相似的折叠方式。HPAMPD通过位于三个关键结构元件中的极性和带电荷残基获得了与AMP的5'-单磷酸基团相互作用的能力：（1）β1链之后的环；（2）αH和αI螺旋之间的环；（3）β5链末端及其相邻环。我们通过将HPAMPD的这些元件整合到另一种相关的软体动物核苷腺苷脱氨酶海兔ADGF中，构建了一种嵌合脱氨酶。该嵌合酶能高效地使AMP脱氨，显示出获得的底物特异性，同时保留了海兔ADGF的腺苷脱氨活性。HPAMPD的磷酸结合特征是核苷酸脱氨酶的一个标志，在AMP和N6-甲基-AMP（6mAMP）脱氨酶中保守。我们讨论了对核苷、核苷酸（AMP）及其甲基化形式6mAMP具有不同底物特异性的人类腺苷脱氨酶。
