Publications

• An aldehyde oxidase in developing seeds of Arabidopsis converts benzaldehyde to benzoic Acid.

  Ibdah M., Chen Y.-T., Wilkerson C.G., Pichersky E.

  Arabidopsis (Arabidopsis thaliana) siliques synthesize high levels of benzoic acid (BA), which is incorporated into several glucosinolate compounds. The origin of BA in the siliques has not yet been determined. Here, we show that siliques have higher levels of benzaldehyde (BD)-oxidizing activity ... >> More

  Arabidopsis (Arabidopsis thaliana) siliques synthesize high levels of benzoic acid (BA), which is incorporated into several glucosinolate compounds. The origin of BA in the siliques has not yet been determined. Here, we show that siliques have higher levels of benzaldehyde (BD)-oxidizing activity relative to leaves. The BD-oxidizing activity was purified from siliques in several chromatographic steps, and a 145-kD protein was identified as the enzyme most likely to possess this activity. The protein was trypsinized, and the sequence of the resulting peptides was determined by mass spectrometry, identifying it as the product of gene At1g04580, also designated as AAO4 (for ARABIDOPSIS ALDEHYDE OXIDASE4). AAO4 had previously been shown to be highly and specifically expressed in developing seeds, and its protein was shown to belong to a family of aldehyde oxidases. Here, we show that the AAO4 protein is an aldehyde oxidase that can use several substrates but that, among the substrates tested, has the lowest K(m) value (23 microm) with BD. AAO4 is able to oxidize BD without NAD(+), but its activity increases by 50% when this cofactor is added. The pH optimum of AAO4 is 7.0. Plants homozygous for a null allele in AAO4 showed a reduction of 30% to 45% in the total levels of BA in seeds as well as 7% to 9% and 32% to 38% decreases in the levels of 3-benzoyloxypropylglucosinolate and 4-benzoyloxybutylglucosinolate, respectively. Expressing AAO4 in Escherichia coli resulted in a 3-fold increase of BD-oxidizing activity in crude bacterial extracts over endogenous levels. These findings indicate that in Arabidopsis seeds, oxidation of BD contributes in part to the synthesis of BA. << Less

  Plant Physiol. 150:416-423(2009) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• ntn genes determining the early steps in the divergent catabolism of 4-nitrotoluene and toluene in Pseudomonas sp. strain TW3.

  James K.D., Williams P.A.

  Pseudomonas sp. strain TW3 is able to oxidatively metabolize 4-nitrotoluene and toluene via a route analogous to the upper pathway of the TOL plasmids. We report the sequence and organization of five genes, ntnWCMAB*, which are very similar to and in the same order as the xyl operon of TOL plasmid ... >> More

  Pseudomonas sp. strain TW3 is able to oxidatively metabolize 4-nitrotoluene and toluene via a route analogous to the upper pathway of the TOL plasmids. We report the sequence and organization of five genes, ntnWCMAB*, which are very similar to and in the same order as the xyl operon of TOL plasmid pWW0 and present evidence that they encode enzymes which are expressed during growth on both 4-nitrotoluene and toluene and are responsible for their oxidation to 4-nitrobenzoate and benzoate, respectively. These genes encode an alcohol dehydrogenase homolog (ntnW), an NAD+-linked benzaldehyde dehydrogenase (ntnC), a two-gene toluene monooxygenase (ntnMA), and part of a benzyl alcohol dehydrogenase (ntnB*), which have 84 to 99% identity at the nucleotide and amino acid levels with the corresponding xylWCMAB genes. The xylB homolog on the TW3 genome (ntnB*) appears to be a pseudogene and is interrupted by a piece of DNA which destroys its functional open reading frame, implicating an additional and as-yet-unidentified benzyl alcohol dehydrogenase gene in this pathway. This conforms with the observation that the benzyl alcohol dehydrogenase expressed during growth on 4-nitrotoluene and toluene differs significantly from the XylB protein, requiring assay via dye-linked electron transfer rather than through a nicotinamide cofactor. The further catabolism of 4-nitrobenzoate and benzoate diverges in that the former enters the hydroxylaminobenzoate pathway as previously reported, while the latter is further metabolized via the beta-ketoadipate pathway. << Less

  J Bacteriol 180:2043-2049(1998) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.