title: Tryptophan metabolism in rabbits.
abstract: Enzyme activities involved in tryptophan metabolism along the kynurenine pathway were studied in male New Zealand white rabbits. Activities are expressed both as specific activity and per g of fresh tissue. Liver tryptophan 2,3-dioxygenase activity (TDO), when assayed in either the absence (holoenzyme) or presence of added haematin (apoenzyme), did not change. Therefore, in rabbit, TDO was present only in holoenzyme form. Small intestine indole 2,3-dioxygenase was significantly higher than liver TDO. Mitochondrial kynurenine 3-monooxygenase was higher in liver than in kidney. Kynureninase activity was similar in both tissues, whereas kynurenine-oxoglutarate transaminase was markedly higher in kidney than in liver. 3-Hydroxyanthranilate 3,4-dioxygenase and aminocarboxymuconate-semialdehyde decarboxylase activities were higher in kidney than in liver. However, the former enzyme showed much higher activity than the latter. These findings suggest that, in rabbit, tryptophan is mainly metabolised along the kynurenine pathway although the apo-TDO enzyme is lacking, as high indole 2,3-dioxygenase activity can obviate this lack.
authors.affiliation: Department of Pharmaceutical Sciences, University of Padova, Via Marzolo 5, I-35131 Padova, Italy. graziella.allegri@unipd.it
authors.forename: Graziella
authors.initials: G
authors.lastname: Allegri
authors.forename: Eugenio
authors.initials: E
authors.lastname: Ragazzi
authors.forename: Antonella
authors.initials: A
authors.lastname: Bertazzo
authors.forename: Monica
authors.initials: M
authors.lastname: Biasiolo
authors.forename: Carlo V L
authors.initials: CV
authors.lastname: Costa
mesh_terms: D000818:Animals; D001051:Apoenzymes / Q000378:metabolism; D020035:Holoenzymes / Q000378:metabolism; D007421:Intestine, Small / Q000201:enzymology; D007668:Kidney / Q000201:enzymology; D007737:Kynurenine / Q000378:metabolism; D050601:Kynurenine 3-Monooxygenase; D008099:Liver / Q000201:enzymology; D008297:Male; D006899:Mixed Function Oxygenases / Q000378:metabolism; D011817:Rabbits; D014364:Tryptophan / Q000378:metabolism*; D014366:Tryptophan Oxygenase / Q000378:metabolism
chemical_list: D001051:Apoenzymes; D020035:Holoenzymes; D007737:Kynurenine; D014364:Tryptophan; D006899:Mixed Function Oxygenases; D014366:Tryptophan Oxygenase; D050601:Kynurenine 3-Monooxygenase