diphthamide-[translation elongation factor 2] + NAD(+) = N-(ADP-D-ribosyl)diphthamide-[translation elongation factor 2] + nicotinamide + H(+)
diphthamide-[translation elongation factor 2] + nad(+) = n-(adp-d-ribosyl)diphthamide-[translation elongation factor 2] + nicotinamide + h(+)