Annotation inferences using phylogenetic trees
Combined Automated Annotation using Multiple IEA Methods
Identification and characterization of genes for a second anthranilate synthase in Pseudomonas aeruginosa: interchangeability of the two anthranilate synthases and evolutionary implications.
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The cloned phnA phnB pair complements E. coli trpE and trpE(G) mutants, establishing anthranilate synthase activity for the gene pair.
"The cloned phnA phnB gene pair complements trpE and trpE(G) mutants of Escherichia coli."
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The pigment phenotype of phn mutants is partial, and residual pyocyanin depends on the tryptophan-pathway anthranilate synthase, which shows that the link to pyocyanin runs through the supply of anthranilate rather than through a dedicated phenazine step.
"Introduction of an inactivated trpE gene into a phnA mutant abolished residual pyocyanin production, suggesting that the trpE trpG gene products are capable of providing some anthranilate for pyocyanin synthesis."
The role of two Pseudomonas aeruginosa anthranilate synthases in tryptophan and quorum signal production.
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The anthranilate made by PhnAB is the precursor of PQS, and the pyocyanin connection is indirect, through PQS-dependent induction of the phenazine genes.
"At the time it was believed that PhnAB generated anthranilate for pyocyanin production, but later work determined that anthranilate is instead a precursor for PQS production, which is required to induce genes for pyocyanin biosynthesis"
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A phnAB deletion makes no detectable PQS under aromatic amino acid growth conditions, and PQS production is restored by feeding anthranilate.
"No detectable PQS was produced by Δ phnAB , indicating that PhnAB is the anthranilate synthase responsible for PQS production in the presence of phenylalanine and tyrosine"
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The two anthranilate synthases of PAO1 differ in expression timing rather than in chemistry, which explains why they do not substitute for one another in vivo.
"At low cell densities PhnAB expression is low and TrpEG is the primary anthranilate synthase enzyme present."
Ligand binding induces an ammonia channel in 2-amino-2-desoxyisochorismate (ADIC) synthase PhzE.
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The first committed enzyme of phenazine biosynthesis, PhzE, converts chorismate and glutamine to ADIC, not to anthranilate, so the phenazine pathway does not consume anthranilate.
"PhzE utilizes chorismate and glutamine to synthesize 2-amino-2-desoxyisochorismate (ADIC) in the first step of phenazine biosynthesis."
The fused TrpEG from Streptomyces venezuelae is an anthranilate synthase, not a 2-amino-2-deoxyisochorismate [corrected] (ADIC) synthase.
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Sequence similarity to PhzE does not imply ADIC synthase activity, and conversely: the anthranilate synthase and ADIC synthase activities must be distinguished experimentally. PhzE is confirmed as the ADIC synthase.
"PhzE has the sequence signature of an anthranilate synthase, but recent evidence indicates that it catalyzes the production of"
Two distinct pathways supply anthranilate as a precursor of the Pseudomonas quinolone signal.
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Anthranilate for PQS can come either from chorismate via an anthranilate synthase or from tryptophan degradation through the kynurenine pathway.
"This compound can be derived from the conversion of chorismate to anthranilate by an anthranilate synthase or through the degradation of tryptophan via the anthranilate branch of the kynurenine pathway."
UniProt entry P09786 (PHNB_PSEAE)
phnB bioinformatics - PAINT node PTN000230115 composition and propagation