Disease relevance of poxB

• Cloning and expression of poxB in Escherichia coli conferred beta-lactam resistance to the host [1].
• The gene was named poxB for Pseudomonas oxacillinase [1].
• Serum reactivity against bacterial pyruvate dehydrogenase: Increasing the specificity of anti-mitochondrial antibodies for the diagnosis of primary biliary cirrhosis [2].

High impact information on poxB

• The predicted structure has significant similarity with the dihydrolipoamide acetyltransferase (EC 2.3.1.12) of the Escherichia coli pyruvate dehydrogenase multienzyme complex [3].
• However, direct and competitive enzyme-linked immunosorbent assays failed to implicate the coenzyme of the pyruvate dehydrogenase complex, lipoic acid or its amide, as the common antigenic moiety [4].
• A thiamin-bound, pre-decarboxylation reaction intermediate analogue in the pyruvate dehydrogenase E1 subunit induces large scale disorder-to-order transformations in the enzyme and reveals novel structural features in the covalently bound adduct [5].
• This pathway was tested by labeling a PDH domain with deuterated octanoate in an E. coli strain devoid of LipA activity [6].
• Recently, one substrate for lipoyl synthase has been shown to be the octanoylated derivative of the lipoyl-bearing subunit (E(2)) of the pyruvate dehydrogenase complex [Zhao, S., Miller, J. R., Jian, Y., Marletta, M. A., and Cronan, J. E., Jr. (2003) Chem. Biol. 10, 1293-1302] [7].

Chemical compound and disease context of poxB

• Molecular cloning of the gene (poxB) encoding the pyruvate oxidase of Escherichia coli, a lipid-activated enzyme [8].
• In an earlier study (S. W. Jordan and J. E. Cronan, Jr., J. Biol. Chem. 272:17903-17906, 1997) we reported a new enzyme, lipoyl-[acyl carrier protein]-protein N-lipoyltransferase, in Escherichia coli and mitochondria that transfers lipoic acid from lipoyl-acyl carrier protein to the lipoyl domains of pyruvate dehydrogenase [9].
• The expressed enzyme in the E. coli mutant efficiently complemented the activity of pyruvate dehydrogenase complex, but less efficiently than that of 2-oxoglutarate dehydrogenase complex [10].

Biological context of poxB

• Two of the smaller poxB plasmids were shown to cause the overproduction of oxidase activity (by six- to eightfold), and one of these plasmids was shown to encode a protein having the size and antigenic determinants of pyruvate oxidase [8].
• It is likely that the apparent pyoverdine-deficient phenotype of mutant OT2100 is a consequence of acidification of the growth medium due to accumulation of pyruvic acid in the absence of functional PDH [11].
• Genetic and biochemical analyses of the mutant revealed the downregulation of many TCA cycle enzymes, including citrate synthase, and the upregulation of the pyruvate dehydrogenase complex in both transcription and enzyme activities [12].
• The results support the view that synthesis of the PDH complex is regulated from the pdhR promoter of a pdhR-aceEF-lpd operon [13].
• Active-site changes in the pyruvate dehydrogenase multienzyme complex E1 apoenzyme component from Escherichia coli observed at 2.32 A resolution [14].

Anatomical context of poxB

• These findings suggest that LIP2p is located in plastids and responsible for lipoylation of the plastidial PDH complex [15].

Associations of poxB with chemical compounds

• Strain YYC202 (aceEF pfl poxB pps) generated 90 g/liter lactate in 16 h during the anaerobic phase (with a yield of 0.95 g/g and a productivity of 5.6 g/liter . h) [16].
• The malic enzyme, involved in the production of pyruvate, and pyruvate dehydrogenase, required for the channelling of pyruvate into acetyl-CoA, were also induced in IAA-treated cells [17].
• Lipoic acid is synthesized from octanoic acid by insertion of sulfur atoms at carbons 6 and 8 and is covalently attached to a pyruvate dehydrogenase (PDH) subunit [6].
• We have detected a very slow LplA-catalyzed transfer of lipoic acid and octanoic acid from their acyl carrier protein thioesters to the lipoyl domain of pyruvate dehydrogenase [9].
• Lipoic acid and NAD are essential cofactors for the activities of pyruvate dehydrogenase complex, 2-oxoglutarate dehydrogenase complex and glycine cleavage enzyme complex [18].

Physical interactions of poxB

• Escherichia coli LipA is a lipoyl synthase: in vitro biosynthesis of lipoylated pyruvate dehydrogenase complex from octanoyl-acyl carrier protein [19].

Other interactions of poxB

• A second gene, aceA, which is likely to encode the E1 component of PDH, was identified upstream from aceB [11].
• Mutants carrying a null mutation in the lipB gene retained a partial ability to synthesize lipoic acid and produced low levels of pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase activities [20].
• Reassociation to a fully active complex molecule works with equal facility between the pyruvate dehydrogenase component and a dihydrolipoamide transacetylase: dihydrolipoamide dehydrogenase subcomplex from either organism in all possible combinations [21].

Analytical, diagnostic and therapeutic context of poxB

• We report mutations generated by chemical and oligonucleotide-mediated site-directed mutagenesis of the poxB gene which result in enzymes defective in lipid activation [22].
• Protein pull-down and bacterial two-hybrid assays followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrospray ionization-tandem mass spectrometry analyses showed the pyruvate dehydrogenase (PDH) E1 subunit as a component interacting with the pirin(Sm) gene [23].
• Structure, expression, and protein engineering of the pyruvate dehydrogenase complex of Escherichia coli [24].

References