This model describes kynureninase, a pyridoxal-phosphate enzyme. Kynurinine is a Trp breakdown product and a precursor for NAD. In Chlamydia psittaci, an obligate intracellular pathogen, kynureninase makes anthranilate, a Trp precursor, from kynurenine. This counters the tryptophan hydrolysis that occurs in the host cell in response to the pathogen. [Energy metabolism, Amino acids and amines]