The four aldehyde oxidases of Drosophila melanogaster have different gene expression patterns and enzyme substrate specificities

Abstract

In the genome of Drosophila melanogaster, four genes coding for aldehyde oxidases (AOX1-4) were identified on chromosome 3. Phylogenetic analysis showed that the AOX gene cluster evolved via independent duplication events in the vertebrate and invertebrate lineages. The functional role and the substrate specificity of the distinct Drosophila AOX enzymes is unknown. Two loss-of-function mutant alleles in this gene region, low pyridoxal oxidase (Po lpo ) and aldehyde oxidase-1 (Aldox-1 n1 ) are associated with a phenotype characterized by undetectable AOX enzymatic activity. However, the genes involved and the corresponding mutations have not yet been identified. In this study we characterized the activities, substrate specificities and expression profiles of the four AOX enzymes in D. melanogaster. We show that the Po lpo -associated phenotype is the consequence of a structural alteration of the AOX1 gene. We identified an 11-bp deletion in the Po lpo allele, resulting in a frameshift event, which removes the molybdenum cofactor domain of the encoded enzyme. Furthermore, we show that AOX2 activity is detectable only during metamorphosis and characterize a Minos-AOX2 insertion in this developmental gene that disrupts its activity. We demonstrate that the Aldox-1 n1 phenotype maps to the AOX3 gene and AOX4 activity is not detectable in our assays.

Disorders affecting vitamin B6 metabolism

“…Early reports suggested that in humans an aldehyde dehydrogenase (EC 1.2.1.4) or aldehyde oxidase (AOX; EC 1.2.3.1) 30 is responsible for this reaction. However, while in Drosophila pyridoxal has been shown to be a substrate of AOX1 31 it is not metabolized by mouse AOXs. 32 For PLP to enter the brain, it must dissociate from albumin and be dephosphorylated to pyridoxal at the blood-brain barrier (BBB).…”

RETRACTED: Chemoprotective role of molybdo-flavoenzymes against xenobiotic compounds

“…In addition to enzyme activities XOR and AO genes have been investigated in several insects. D. melanogaster has one XDH and four AO (AOX 1-4) genes were identified on chromosome 3 (Garattini et al, 2003;Marelja et al, 2014). The evolution of the AOX genes was determined and phylogenetic analysis showed that the AOX gene cluster evolved via independent duplication events in the vertebrate and invertebrate lineages (Marelja et al, 2014).…”

“…D. melanogaster has one XDH and four AO (AOX 1-4) genes were identified on chromosome 3 (Garattini et al, 2003;Marelja et al, 2014). The evolution of the AOX genes was determined and phylogenetic analysis showed that the AOX gene cluster evolved via independent duplication events in the vertebrate and invertebrate lineages (Marelja et al, 2014). Recently, Marelja et al, 2014 have reported that pyridoxal oxidase is the product of the Drosophila AOX1 gene.…”

Direct Comparison of the Enzymatic Characteristics and Superoxide Production of the Four Aldehyde Oxidase Enzymes Present in Mouse

“…Surprisingly and contrary to the idea that AOXs are involved in the metabolism of vitamin B6 [Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, http://www.genome.jp/kegg], pyridoxal is not recognized as a substrate by any of the four mouse AOX enzymes. To confirm this important observation, we further evaluated the ability of mAOX1, mAOX3, mAOX4, and mAOX2 to oxidize pyridoxal, using as a basis an active enzyme staining assay with native polyacrylamide gel electrophoresis under nonreducing conditions (Marelja et al, 2014). In fact, this assay allows long incubation times with the selected AOX substrate and it is characterized by an unmatched level of sensitivity under these experimental conditions.…”