This is a known occurrence, and it has been suggested that this fall in Gln during hyperammonemia, quite unlike the increase seen in urea cycle deficiency patients, might be caused by the inhibition of glutamine synthetase due to the excess presence of propionyl-CoA or the highly toxic methyl citrate (Filipowicz et al. 2006; Al-Hassnan et al. 2003; Ierardi-Curto et al. 2000). Here, GLUL is linked to Hyperammonemia.