Avian and mammalian mitochondrial ammonia-detoxifying systems in tortoise liver

摘要: Liver mitochondria from the desert tortoise Gopherus agassizii and Texas G. berlandieri contain glutamine synthetase, enzyme used by birds higher reptiles to detoxify ammonia generated intramitochondrially during amino acid catabolism. Tortoise also carbamyl phosphate synthetase-I ornithine transcarbamylase, enzymes mammals for this purpose. Since chelonid have changed little since their divergence stem reptiles, finding suggests that both systems were present in latter before emergence of ruling reptile, avian, mammalian lines descent.