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Arginine catabolism enzyme AgrE/ArgZ likely involves a cyanobacterial specific factor

Open AccessPublished:March 06, 2020DOI:https://doi.org/10.1074/jbc.L120.012850

      Introduction

      Arginine is a proteinaceous amino acid that is also used in numerous metabolic processes, which is reflected in the presence of numerous different arginine utilization pathways in nature. In cyanobacteria, a novel enzyme showing arginine dihydrolase activity has recently been found and named ArgZ in Synechocystis (
      • Zhang H.
      • Liu Y.
      • Nie X.
      • Liu L.
      • Hua Q.
      • Zhao G.P.
      • Yang C.
      The cyanobacterial ornithine-ammonia cycle involves an arginine dihydrolase.
      ) or AgrE in Anabaena (
      • Burnat M.
      • Picossi S.
      • Valladares A.
      • Herrero A.
      • Flores E.
      Catabolic pathway of arginine in Anabaena involves a novel bifunctional enzyme that produces proline from arginine.
      ). (AgrE stands for arginine-guanidine–removing enzyme.) Zhuang et al. (
      • Zhuang N.
      • Zhang H.
      • Li L.
      • Wu X.
      • Yang C.
      • Zhang Y.
      Crystal structures and biochemical analyses of the bacterial arginine dihydrolase ArgZ suggests a “bond-rotation” catalytic mechanism.
      ) have reported the crystal structure of Synechocystis ArgZ, showing that amino acid residues 1–269 form an α/β propeller domain characteristic of guanidine group–modifying enzymes and describing the catalytic mechanism that removes two ammonia molecules and one CO2 molecule from arginine, producing ornithine. ArgZ/AgrE consists of ∼700 amino acids, and its C-terminal part (amino acid residues 285–700) is homologous to a Methanococcus maripaludis protein annotated as lysine-oxoglutarate reductase/saccharopine dehydrogenase. Genetic-biochemical analysis of Anabaena AgrE and of M. maripaludis protein MMP1218 expressed in Anabaena has demonstrated that MMP1218 and the C-terminal part of AgrE show ornithine cyclodeaminase activity (
      • Burnat M.
      • Picossi S.
      • Valladares A.
      • Herrero A.
      • Flores E.
      Catabolic pathway of arginine in Anabaena involves a novel bifunctional enzyme that produces proline from arginine.
      ). Thus, AgrE is a bifunctional enzyme that sequentially transforms arginine → ornithine → proline. This enzyme is essential for full arginine catabolism in cyanobacteria (
      • Burnat M.
      • Picossi S.
      • Valladares A.
      • Herrero A.
      • Flores E.
      Catabolic pathway of arginine in Anabaena involves a novel bifunctional enzyme that produces proline from arginine.
      ,
      • Flores E.
      • Arévalo S.
      • Burnat M.
      Cyanophycin and arginine metabolism in cyanobacteria.
      ) rather than being important only as an arginine dihydrolase (
      • Zhang H.
      • Liu Y.
      • Nie X.
      • Liu L.
      • Hua Q.
      • Zhao G.P.
      • Yang C.
      The cyanobacterial ornithine-ammonia cycle involves an arginine dihydrolase.
      ). Zhuang et al. (
      • Zhuang N.
      • Zhang H.
      • Li L.
      • Wu X.
      • Yang C.
      • Zhang Y.
      Crystal structures and biochemical analyses of the bacterial arginine dihydrolase ArgZ suggests a “bond-rotation” catalytic mechanism.
      ) were unable, however, to ascribe any function to the C-terminal part of ArgZ. Because only the enzyme isolated from Anabaena showed ornithine cyclodeaminase activity (
      • Burnat M.
      • Picossi S.
      • Valladares A.
      • Herrero A.
      • Flores E.
      Catabolic pathway of arginine in Anabaena involves a novel bifunctional enzyme that produces proline from arginine.
      ) and Zhuang et al. crystalized the enzyme cloned in Escherichia coli (
      • Zhuang N.
      • Zhang H.
      • Li L.
      • Wu X.
      • Yang C.
      • Zhang Y.
      Crystal structures and biochemical analyses of the bacterial arginine dihydrolase ArgZ suggests a “bond-rotation” catalytic mechanism.
      ), I suggest that a cyanobacterial factor is missing from the enzyme that was crystalized.

      References

        • Zhang H.
        • Liu Y.
        • Nie X.
        • Liu L.
        • Hua Q.
        • Zhao G.P.
        • Yang C.
        The cyanobacterial ornithine-ammonia cycle involves an arginine dihydrolase.
        Nat. Chem. Biol. 2018; 14 (29632414): 575-581
        • Burnat M.
        • Picossi S.
        • Valladares A.
        • Herrero A.
        • Flores E.
        Catabolic pathway of arginine in Anabaena involves a novel bifunctional enzyme that produces proline from arginine.
        Mol. Microbiol. 2019; 111 (30636068): 883-897
        • Zhuang N.
        • Zhang H.
        • Li L.
        • Wu X.
        • Yang C.
        • Zhang Y.
        Crystal structures and biochemical analyses of the bacterial arginine dihydrolase ArgZ suggests a “bond-rotation” catalytic mechanism.
        J. Biol. Chem. 2019; 295 (31914412): 2113-2124
        • Flores E.
        • Arévalo S.
        • Burnat M.
        Cyanophycin and arginine metabolism in cyanobacteria.
        Algal Res. 2019; 42101577