Catalyzes the hydroxylation of L-kynurenine (L-Kyn) to form 3-hydroxy-L-kynurenine (L-3OHKyn). Required for synthesis of quinolinic acid. H(+) + L-kynurenine + NADPH + O2 = 3-hydroxy-L-kynurenine + H2O + NADP(+) Cofactor biosynthesis; NAD(+) biosynthesis; quinolinate from L-kynurenine: step 1/3. Belongs to the aromatic-ring hydroxylase family. KMO subfamily.