Identification of the function of the metabolite repair enzyme Nit1: the story of a collaboration with Arthur Cooper

Nit1 and Nit2 were initially identified in the context of cancer research, as proteins encoded by putative (anti)oncogenes. However, the presence of homologous proteins in bacteria suggested that they might be enzymes with a fundamental metabolic function. Our group, while interacting with Arthur Cooper and his collaborators, contributed to uncovering these roles: Nit2 was identified in 2009 as an omega-amidase, the enzyme that hydrolyses the 'omega' amide of alpha-ketoglutaramate and alpha-ketosuccinamate, the 'deaminated' derivatives of glutamine and asparagine produced in some irreversible transamination reactions. Later, in 2017, we showed that Nit1 functions as a metabolite-repair enzyme. Specifically, Nit1 efficiently hydrolyzes deaminated gluthathione (dGSH), a non-functional byproduct generated by a side activity of various classical transaminases. This repair function prevents the accumulation of the useless metabolite dGSH. The physiological significance of Nit1 is underscored by recent discoveries linking its deficiency in humans to a neurological disorder.