Isolation and expression of a cDNA clone encoding human kynureninase

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Kynureninase (L-kynurenine hydrolase) is a pyridoxal-5'-phosphate-dependent enzyme.
• It catalyzes the conversion of L-kynurenine and L-3-hydroxykynurenine into anthranilic and 3-hydroxyanthranilic acids.
• Understanding human kynureninase is vital for metabolic pathway research.

Purpose of the Study:

• To isolate and characterize the cDNA clone encoding human kynureninase.
• To analyze the structural and functional properties of the human kynureninase enzyme.
• To investigate the expression patterns of human kynureninase mRNA in various tissues.

Main Methods:

• Degenerate oligonucleotides and reverse-transcription PCR were used to amplify rat kynureninase cDNA.
• A human hepatoma cell line (Hep G2) cDNA library was screened using the rat cDNA.
• Sequence analysis, RNA blot analysis, and enzyme kinetics studies (K(m) determination) were performed.

Main Results:

• A 1651-nucleotide cDNA clone encoding human kynureninase (456 amino acids) was isolated.
• The predicted amino acid sequence showed high similarity to rat and yeast counterparts.
• Functional analysis confirmed the presence of a pyridoxal-P binding site and determined kinetic parameters for L-kynurenine and DL-3-hydroxykynurenine.

Conclusions:

• The successful isolation and characterization of human kynureninase cDNA provide a foundation for further functional studies.
• The findings reveal conserved structural features and enzymatic activity, relevant to tryptophan metabolism.
• Expression analysis indicates widespread distribution of kynureninase mRNA in human tissues, including the brain.