Leibniz Universität Hannover, Department of Molecular Nutrition and Biochemistry of Plants, Herrenhäuser Strasse 2, 30419, Hannover, Germany.
Seoul National University, Department of Agricultural Biotechnology, 151-921, Seoul, Republic of Korea.
Nat Commun. 2021 Nov 25;12(1):6846. doi: 10.1038/s41467-021-27152-4.
In plants, guanosine monophosphate (GMP) is synthesized from adenosine monophosphate via inosine monophosphate and xanthosine monophosphate (XMP) in the cytosol. It has been shown recently that the catabolic route for adenylate-derived nucleotides bifurcates at XMP from this biosynthetic route. Dephosphorylation of XMP and GMP by as yet unknown phosphatases can initiate cytosolic purine nucleotide catabolism. Here we show that Arabidopsis thaliana possesses a highly XMP-specific phosphatase (XMPP) which is conserved in vascular plants. We demonstrate that XMPP catalyzes the irreversible entry reaction of adenylate-derived nucleotides into purine nucleotide catabolism in vivo, whereas the guanylates enter catabolism via an unidentified GMP phosphatase and guanosine deaminase which are important to maintain purine nucleotide homeostasis. We also present a crystal structure and mutational analysis of XMPP providing a rationale for its exceptionally high substrate specificity, which is likely required for the efficient catalysis of the very small XMP pool in vivo.
在植物中，鸟苷一磷酸（GMP）是通过肌苷一磷酸和黄苷一磷酸（XMP）在细胞质中从腺苷一磷酸合成的。最近的研究表明，腺嘌呤衍生核苷酸的分解途径在 XMP 处从这个生物合成途径分叉。XMP 和 GMP 的去磷酸化由目前尚不清楚的磷酸酶可以启动细胞质嘌呤核苷酸分解代谢。在这里，我们展示了拟南芥（Arabidopsis thaliana）拥有一种高度特异性的 XMP 磷酸酶（XMPP），这种酶在维管植物中是保守的。我们证明，XMPP 催化腺嘌呤衍生核苷酸不可逆地进入体内嘌呤核苷酸分解代谢的入口反应，而鸟苷酸则通过一种未鉴定的 GMP 磷酸酶和鸟苷脱氨酶进入分解代谢，这对于维持嘌呤核苷酸的体内平衡是重要的。我们还展示了 XMPP 的晶体结构和突变分析，为其异常高的底物特异性提供了依据，这可能是体内非常小的 XMP 池高效催化所必需的。
