KMO(Kynurenine 3-monooxygenase) is an NADPH-dependent flavin monooxygenase,catalysing the hydroxylation of the L-tryptophan metabolite L-kynurenine to form L-3-hydroxykynurenine. KMO is a membrane protein located on the outer membrane of mitochondria. Tissue distribution studies have revealed that,in rats,highest enzyme activity is found in kidney and liver,with brain having the least activity in comparison to peripheral organs.