title: Kynureninase-Type enzymes of Penicillum roqueforti, Aspergillus niger, Rhizopus stolonifer, and Pseudomonas fluorescens: further evidence for distinct kynureninase and hydroxykynureninase activities.
abstract: The kynureninase-type enzymes of three fungi and one bacterium were isolated and examined kinetically for their ability to catalyze the hydrolysis of L-kynurenine and L-3-hydroxykynurenine. The phycomycete Rhizopus stolonifer was found to contain a single, constitutive enzyme with Km for L-3-hydroxykynurenine and L-kynurenine of 6.67 times 10-minus 6 and 2.5 times 10-minus 4 M, respectively. The ascomycetes Aspergillus niger and Penicillium roqueforti each contain an enzyme, induced by L-tryptophan, with similar Km for L-3-hydroxykynurenine and L-kynurenine ranging from 5.9 times 10-minus 5 to 14.3 times 10-minus 5 M, as well as a constitutive enzyme with Km for the two substrates of similar to 4 times 10-minus 6 M and 10-minus 4 M. The bacterium Pseudomonas fluorescens has a single, inducible enzyme with Km for L-3-hydroxykynurenine and L-kynurenine of 5 times 10-minus 4 and 7 times 10-minus 5 M. In addition, significant differences in maximal velocities (Vmax) were observed in two cases. The Vmax of the inducible activity from P. fluorescens was 4.5 times greater for L-kynurenine than L-3-hydroxykynurenine, whereas the Vmax of the constitutive activity from R. stolonifer was 2.5 times greater for L-3-hydroxykynurenine. It is concluded (i) that the constitutive activities are hydroxykynureninases involved in the biosynthesis of nicotinamide adenine dinucleotide from L-tryptophan, (ii) that the inducible activities are kynureninases involved in the catabolism of L-tryptophan to anthranilate, and (iii) that R. stolonifer and P. fluorescens, respectively, carry the most specific examples of each type of enzyme.
mesh_terms: D000645:Ammonium Sulfate; D001230:Aspergillus / Q000201:enzymology* / Q000378:metabolism; D002458:Cell Fractionation; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D004790:Enzyme Induction; D006867:Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D006900:Hydroxylation; D007737:Kynurenine / Q000378:metabolism; D009243:NAD / Q000096:biosynthesis; D010407:Penicillium / Q000201:enzymology* / Q000378:metabolism; D011479:Protamines; D011551:Pseudomonas fluorescens / Q000201:enzymology* / Q000378:metabolism; D012233:Rhizopus / Q000201:enzymology* / Q000378:metabolism; D013045:Species Specificity; D014364:Tryptophan / Q000378:metabolism; D062367:ortho-Aminobenzoates / Q000096:biosynthesis
chemical_list: D011479:Protamines; D062367:ortho-Aminobenzoates; D009243:NAD; D007737:Kynurenine; D014364:Tryptophan; D006867:Hydrolases; D000645:Ammonium Sulfate