The enzyme glutamine synthetase (GS) has a central role in cellular nitrogen metabolism. By carrying out the ATP-dependent formation of glutamine from ammonia and glutamate, GS detoxifies ammonia and conveys nitrogen for urea, amino acid and nucleotide biosynthesis. In the May Journal of Experimental Biology, Patrick Walsh and colleagues at the University of Miami, Florida, US, describe intriguing new features of the enzyme from Gulf toadfish (Opsanus beta), and reveal that despite previous intense study GS still holds many secrets (Journal of Experimental Biology, 206:1523-1533, May 1, 2003).

Walsh et al. focused on nitrogen metabolism in the toadfish as it can facultatively excrete nitrogen as ammonia (ammonotely) or as urea (ureotely). They assessed GS enzymatic activity and scrutinized mRNA in several key tissues for general and nitrogen metabolism throughout the animal. Analysis of the PCR-derived sequences of the extracted mRNA revealed — in addition...

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