Publications

• 3-Hydroxykynurenine transaminase identity with alanine glyoxylate transaminase. A probable detoxification protein in Aedes aegypti.

  Han Q., Fang J., Li J.

  This study describes the functional characterization of a specific mosquito transaminase responsible for catalyzing the transamination of 3-hydroxykynurenine (3-HK) to xanthurenic acid (XA). The enzyme was purified from Aedes aegypti larvae by ammonium sulfate fractionation, heat treatment, and va ... >> More

  This study describes the functional characterization of a specific mosquito transaminase responsible for catalyzing the transamination of 3-hydroxykynurenine (3-HK) to xanthurenic acid (XA). The enzyme was purified from Aedes aegypti larvae by ammonium sulfate fractionation, heat treatment, and various chromatographic techniques, plus non-denaturing electrophoresis. The purified transaminase has a relative molecular mass of 42,500 by SDS-PAGE. N-terminal and internal sequencing of the purified protein and its tryptic fragments resolved a partial N-terminal sequence of 19 amino acid residues and 3 partial internal peptide sequences with 7, 10, and 7 amino acid residues. Using degenerate primers based on the partial internal sequences for PCR amplification and cDNA library screening, a full-length cDNA clone with a 1,167-bp open reading frame was isolated. Its deduced amino acid sequence consists of 389 amino acid residues with a predicted molecular mass of 43,239 and shares 45-46% sequence identity with mammalian alanine glyoxylate transaminases. Northern analysis shows the active transcription of the enzyme in larvae and developing eggs. Substrate specificity analysis of this mosquito transaminase demonstrates that the enzyme is active with 3-HK, kynurenine, or alanine substrates. The enzyme has greater affinity and catalytic efficiency for 3-HK than for kynurenine and alanine. The biochemical characteristics of the enzyme in conjunction with the profiles of 3-HK transaminase activity and XA accumulation during mosquito development clearly point out its physiological function in the 3-HK to XA pathway. Our data suggest that the mosquito transaminase was evolved in a manner precisely reflecting the physiological requirement of detoxifying 3-HK produced in the tryptophan oxidation pathway in the mosquito. << Less

  J. Biol. Chem. 277:15781-15787(2002) [PubMed] [EuropePMC]

  This publication is cited by 9 other entries.

• Identification and biochemical characterization of the Anopheles gambiae 3-hydroxykynurenine transaminase.

  Rossi F., Lombardo F., Paglino A., Cassani C., Miglio G., Arca B., Rizzi M.

  Spontaneous oxidation of 3-hydroxykynureine (3-HK), a metabolic intermediate of the tryptophan degradation pathway, elicits a remarkable oxidative stress response in animal tissues. In the yellow fever mosquito Aedes aegypti the excess of this toxic metabolic intermediate is efficiently removed by ... >> More

  Spontaneous oxidation of 3-hydroxykynureine (3-HK), a metabolic intermediate of the tryptophan degradation pathway, elicits a remarkable oxidative stress response in animal tissues. In the yellow fever mosquito Aedes aegypti the excess of this toxic metabolic intermediate is efficiently removed by a specific 3-HK transaminase, which converts 3-HK into the more stable compound xanthurenic acid. In anopheline mosquitoes transmitting malaria, xanthurenic acid plays an important role in Plasmodium gametocyte maturation and fertility. Using the sequence information provided by the Anopheles gambiae genome and available ESTs, we adopted a PCR-based approach to isolate a 3-HK transaminase coding sequence from the main human malaria vector A. gambiae. Tissue and developmental expression analysis revealed an almost ubiquitary profile, which is in agreement with the physiological role of the enzyme in mosquito development and 3-HK detoxification. A high yield procedure for the expression and purification of a fully active recombinant version of the protein has been developed. Recombinant A. gambiae 3-HK transaminase is a dimeric pyridoxal 5'-phosphate dependent enzyme, showing an optimum pH of 7.8 and a comparable catalytic efficiency for both 3-HK and its immediate catabolic precursor kynurenine. This study may be useful for the identification of 3-HK transaminase inhibitors of potential interest as malaria transmission-blocking drugs or effective insecticides. << Less

  FEBS J. 272:5653-5662(2005) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.

• Cysteine and keto acids modulate mosquito kynurenine aminotransferase catalyzed kynurenic acid production.

  Han Q., Li J.

  Kynurenine aminotransferase (KAT) catalyzes the formation of kynurenic acid (KYNA), the natural antagonist of ionotropic glutamate receptors. This study tests potential substrates and assesses the effects of amino acids and keto acids on the activity of mosquito KAT. Various keto acids, when simul ... >> More

  Kynurenine aminotransferase (KAT) catalyzes the formation of kynurenic acid (KYNA), the natural antagonist of ionotropic glutamate receptors. This study tests potential substrates and assesses the effects of amino acids and keto acids on the activity of mosquito KAT. Various keto acids, when simultaneously present in the same reaction mixture, display a combined effect on KAT catalyzed KYNA production. Moreover, methionine and glutamine show inhibitory effects on KAT activity, while cysteine functions as either an antagonist or an inhibitor depending on the concentration. Therefore, the overall level of keto acids and cysteine might modulate the KYNA synthesis. Results from this study will be useful in the study of KAT regulation in other animals. << Less

  FEBS Lett. 577:381-385(2004) [PubMed] [EuropePMC]

  This publication is cited by 28 other entries.