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Kynurenine 3-monooxygenase (KMO) catalyses the hydroxylation of kynurenine to 3-hydroxykynurenine. KMO has a key role in tryptophan catabolism and synthesis of ommochrome pigments in mosquitoes. The gene encoding this enzyme in the yellow fever mosquito, Aedes aegypti, is called kynurenine hydroxylase (kh) and a mutant allele that produces white eyes has been designated khw. A number of cDNA clones representative of wild-type and mutant genes were isolated. Sequence analyses of the wild-type and mutant cDNAs revealed a deletion of 162 nucleotides in the mutant gene near the 3'-end of the deduced coding region. RT-PCR analyses confirm the transcription of a truncated mRNA in the mutant strain. The in-frame deletion results in a loss of 54 amino acids, which disrupts a major alpha-helix and which probably accounts for the loss of activity of the enzyme. Recombinant Ae. aegypti KMO showed high substrate specificity for kynurenine with optimum activity at 40 degrees C and pH = 7.5. Kinetic parameters and inhibition of KMO activity by Cl- and pyridoxal-5-phosphate were determined.

Original publication




Journal article


Insect Mol Biol

Publication Date





483 - 490


Aedes, Animals, DNA, Complementary, Electrophoresis, Polyacrylamide Gel, Gene Deletion, Gene Expression Profiling, Kinetics, Kynurenine 3-Monooxygenase, Mixed Function Oxygenases, Reverse Transcriptase Polymerase Chain Reaction, Sequence Alignment