TY - JOUR

T1 - AMP and GMP Catabolism in Arabidopsis Converge on Xanthosine, Which Is Degraded by a Nucleoside Hydrolase Heterocomplex

AU - Baccolini, Chiara

AU - Witte, Claus-Peter

N1 - Funding Information: We thank André Specht and Hildegard Thölke for technical support, Anting Zhu for generating pXNS2cpmv-Strep (V90), Nieves Medina Escobar for generating pXNS2pat-myc (V103), and Lennart Doering for performing the site-directed mutagenesis of NSH1 and NSH2. We also thank Marc Heins, Sebastian Hoffmann, Sue Genschmer, Manuel Maidorn, Robin Meier, Vincenzo Puggioni, Jana Scharnberg, Anne Taraschewski, and Anting Zhu for generating and screening the double and triple Arabidopsis mutants used in thisstudy.Thisworkwas financiallysupportedbytheDeutscheForschungs-gemeinschaft (grants WI3411/2-1 and WI3411/4-1) and the German Academic Exchange Service (DAAD full PhD fellowship to C.B.).

PY - 2019/3

Y1 - 2019/3

N2 - Plants can fully catabolize purine nucleotides. A firmly established central intermediate is the purine base xanthine. In the current widely accepted model of plant purine nucleotide catabolism, xanthine can be generated in various ways involving either inosine and hypoxanthine or guanosine and xanthosine as intermediates. In a comprehensive mutant analysis involving single and multiple mutants of urate oxidase, xanthine dehydrogenase, nucleoside hydrolases, guanosine deaminase, and hypoxanthine guanine phosphoribosyltransferase, we demonstrate that purine nucleotide catabolism in Arabidopsis (Arabidopsis thaliana) mainly generates xanthosine, but not inosine and hypoxanthine, and that xanthosine is derived from guanosine deamination and a second source, likely xanthosine monophosphate dephosphorylation. Nucleoside hydrolase 1 (NSH1) is known to be essential for xanthosine hydrolysis, but the in vivo function of a second cytosolic nucleoside hydrolase, NSH2, is unclear. We demonstrate that NSH1 activates NSH2 in vitro and in vivo, forming a complex with almost two orders of magnitude higher catalytic efficiency for xanthosine hydrolysis than observed for NSH1 alone. Remarkably, an inactive NSH1 point mutant can activate NSH2 in vivo, fully preventing purine nucleoside accumulation in nsh1 background. Our data lead to an altered model of purine nucleotide catabolism that includes an NSH heterocomplex as a central component.

AB - Plants can fully catabolize purine nucleotides. A firmly established central intermediate is the purine base xanthine. In the current widely accepted model of plant purine nucleotide catabolism, xanthine can be generated in various ways involving either inosine and hypoxanthine or guanosine and xanthosine as intermediates. In a comprehensive mutant analysis involving single and multiple mutants of urate oxidase, xanthine dehydrogenase, nucleoside hydrolases, guanosine deaminase, and hypoxanthine guanine phosphoribosyltransferase, we demonstrate that purine nucleotide catabolism in Arabidopsis (Arabidopsis thaliana) mainly generates xanthosine, but not inosine and hypoxanthine, and that xanthosine is derived from guanosine deamination and a second source, likely xanthosine monophosphate dephosphorylation. Nucleoside hydrolase 1 (NSH1) is known to be essential for xanthosine hydrolysis, but the in vivo function of a second cytosolic nucleoside hydrolase, NSH2, is unclear. We demonstrate that NSH1 activates NSH2 in vitro and in vivo, forming a complex with almost two orders of magnitude higher catalytic efficiency for xanthosine hydrolysis than observed for NSH1 alone. Remarkably, an inactive NSH1 point mutant can activate NSH2 in vivo, fully preventing purine nucleoside accumulation in nsh1 background. Our data lead to an altered model of purine nucleotide catabolism that includes an NSH heterocomplex as a central component.

UR - http://www.scopus.com/inward/record.url?scp=85064975800&partnerID=8YFLogxK

U2 - 10.1105/tpc.18.00899

DO - 10.1105/tpc.18.00899

M3 - Article

VL - 31

SP - 734

EP - 751

JO - The plant cell

JF - The plant cell

SN - 1040-4651

IS - 3

ER -