ADP-ribosyltransferase that targets a specific class of NAD(+)-dependent glutamate dehydrogenase (GDH) enzymes found in fungi and protists, including many natural hosts of Legionella. Acts by targeting a conserved arginine residue in the NAD(+)-binding pocket of GDH, thereby blocking oxidative deamination of glutamate. Lart1 may target amoeba GDH to prevent a conserved stress response. In vitro, acts on Glud2 from the amoeba Dictyostelium discoideum (DdGluD2) and yeast Gdh2p but does not act on human or Legionella GDH homologs. L-arginyl-[protein] + NAD(+) = H(+) + N(omega)-(ADP-D-ribosyl)-L-arginyl-[protein] + nicotinamide kcat is 0.11 min(-1) with DdGluD2 as substrate. kcat is 0.15 min(-1) with NAD(+) as substrate. Optimum pH is 6.0. Translocated into the host cell via the type IV secretion system (T4SS). Deletion of the gene has no effect on bacterial replication in the amoeba A.castellani.