Direct evidence for a tryptophan-anthranilic acid cycle in Neurospora

Formation of N-acetylaminophenol from anthranilic acid by Pseudomonas pyrrocinia ATCC15958

“…Anthranilic acid is an intermediary metabolite in both biosynthetic and catabolic pathways in microorganisms [1,2]. Anthranilic acid is degraded by most bacteria through catechol [3][4][5].…”

“…Metabolite II was identified as Nacetylanthranilic acid [2]. The Rf-values in TLC of metabolite II and authentic N-acetylanthranilic acid in eluent I and II are identical: R/in eluent I = 0.38, R/in eluent II = 0.67.…”

Occurrence ofN-Formylkynurenine in Extracts ofNeurospora crassa: Evidence for the Activity of Tryptophan Pyrrolase

“…Investigations with mammals and bacteria have shown that the first step in the oxidative degradation of tryptophan is catalyzed by the enzyme tryptophan pyrrolase and that N-formylkynurenine is the product of this reaction (9,13,18). The same reaction has been postulated to occur in Neurospora on the basis of isotope experiments (17) and enzyme studies (10,11,23). From these and other observations (2,8,12,19,20,25) it was postulated that oxidative degradation of tryptophan in Neurospora starts with the formation of N-formylkynurenine.…”

“…From these and other observations (2,8,12,19,20,25) it was postulated that oxidative degradation of tryptophan in Neurospora starts with the formation of N-formylkynurenine. Further metabolic transformation of this compound was proposed to result in the tryptophan-anthranilic acid cycle (17) and the synthesis of niacin (20). A schematic representation of some of these reactions is presented in Fig.…”

Kynureninase-type enzymes from two strains of Xanthomonas pruni

“…In the sequence of nine enzyme-catalyzed reactions which lead to the biosynthetic transformation of L-tryptophan to the pyridine nucleus of nicotinamide adenine dinucleotide (NAD), we have recently shown in a variety of eukaryotes that the fourth step in the pathway, the hydrolysis of L-3-hydroxykynurenine to 3-hydroxyanthranilate, is catalyzed by a specific constitutive enzyme, which we have characterized as a hydroxykynureninase [1 ]. Alternatively, in some organisms, L-tryptophan is catabolically diverted to anthranilate which is subsequently excreted [2], reused in the biosynthesis of L-tryptophan [3], or converted to other metabolites [2]. In a variety of microorganisms, this catabolic diversion is catalyzed by an inducible enzyme that hydrolyzes L-kynurenine or L-3.hydroxykynurenine to anthranilate or 3hydroxyanthranilate [4].…”