Studies on some tryptophan-degrading enzymes in fish
1994
Serrano, A.E. Jr. (Philippines Univ. in the Visayas, Leganes, Iloilo (Philippines). Coll. of Fisheries)
For the purpose of clarifying tryptophan degradation in fish, four liver enzymes were studied. First, tryptophan pyrrolase of rainbow trout was partially purified by a four-step process, and conditions of assay were optimized. Methylene blue, ascorbic acid, hermatin, EDTA, and Ca failed to activate the fish enzyme in the crude liver extracts. Second, Arylformaidase activities were in this decreasing order: grass carp, common carp, rainbow trout, yellowtail, and tilapia. The rainbow trout and cattle enzymes were purified for the first time in these species, and were subsequently characterized. Third, activity and inactivation of 3-hydroxyanthranilic acid oxygenase (3HAA) in rainbow trout were studied. The 3HAA activity could be recovered by heat with ferrous sulfate, singly or in combination with glutathione. Fourth, tryptophan 5-monooxygenase (or tryptophan hydrolase) activities in various fish species were in the following decreasing order: grass carp tilapia and common carp rainbow trout. Km values and optimal pH were also determined for the various fish species. On the whole, it appears that the importance of the serotonin pathway exceeds that of the kynurenine pathway, at least in rainbow trout
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