Catalyzes the hydroxylation of L-kynurenine (L-Kyn) to form 3-hydroxy-L-kynurenine (L-3OHKyn). Probably required for the synthesis of quinolinic acid and the siderophore quinolobactin. H(+) + L-kynurenine + NADPH + O2 = 3-hydroxy-L-kynurenine + H2O + NADP(+) kcat is 2.3 sec(-1) for L-kynurenine. Optimum pH is 8.5. Cofactor biosynthesis; NAD(+) biosynthesis; quinolinate from L-kynurenine: step 1/3. Siderophore biosynthesis; quinolobactin biosynthesis. Belongs to the aromatic-ring hydroxylase family. KMO subfamily.