<jats:p> (i) <jats:italic>Saccharomyces cerevisiae</jats:italic> grown in the presence of 1.0 mM <jats:sc>l</jats:sc> -tryptophan slowly excreted fluorescent material that was chromatographically identifiable as 3-hydroxyanthranilate but did not excrete detectable amounts of anthranilate nor rapidly deplete the medium of <jats:sc>l</jats:sc> -tryptophan. Under similar growth conditions, <jats:italic>Neurospora crassa</jats:italic> rapidly excretes anthranilate and rapidly depletes the medium of <jats:sc>l</jats:sc> -tryptophan. (ii) Chromatographic analysis of crude extracts from yeast revealed a single kynureninase-type enzyme whose synthesis was not measurably affected by the presence of tryptophan in the medium. Previous studies have provided evidence for two kynureninase-type enzymes in <jats:italic>N. crassa</jats:italic> , an inducible kynureninase and a constitutive hydroxykynureninase. (iii) Kinetic analysis of the partially purified yeast enzyme provided Michaelis constants for <jats:sc>l</jats:sc> -3-hydroxykynurenine and <jats:sc>l</jats:sc> -kynurenine of 6.7 × 10 <jats:sup>−6</jats:sup> and 5.4 × 10 <jats:sup>−4</jats:sup> M, respectively. This and other kinetic properties of the yeast enzyme are comparable to those reported for the constitutive enzyme from <jats:italic>N. crassa</jats:italic> . (iv) These findings suggest that <jats:italic>S. cerevisiae</jats:italic> has in common with <jats:italic>N. crassa</jats:italic> the biosynthetic enzyme hydroxykynureninase but lacks the catabolic enzyme kynureninase. Therefore, it can be predicted that, unlike <jats:italic>N. crassa, S. cerevisiae</jats:italic> does not carry out the tryptophan-anthranilate cycle. Distinct kynureninase-type enzymes may exist in other microorganisms and in mammals.