Disease relevance of aceA

• Isolation, hyperexpression, and sequencing of the aceA gene encoding isocitrate lyase in Escherichia coli [1].
• Cloning, heterologous expression and purification of an isocitrate lyase from Streptomyces clavuligerus NRRL 3585 [2].
• Glyoxylate bypass enzymes in Yersinia species and multiple forms of isocitrate lyase in Yersinia pestis [3].
• In this study, the aceA gene product expressed by Acetobacter xylinum, which is involved in the biosynthesis of the exopolysaccharide acetan, was overproduced in Escherichia coli and its function was characterised [4].
• Isocitrate lyase of the facultative intracellular pathogen Rhodococcus equi [5].

High impact information on aceA

• This is a bypass of the tricarboxylic acid cycle in which isocitrate lyase and malate synthase (GlcB) catalyze the net incorporation of carbon during growth of microorganisms on acetate or fatty acids as the primary carbon source [6].
• Evidence of histidine phosphorylation in isocitrate lyase from Escherichia coli [7].
• Treatment of isocitrate lyase with diethyl pyrocarbonate, a histidine-modifying reagent, blocked incorporation of [32P]phosphate from [gamma-32P]ATP [7].
• Immunoprecipitated 32P-labeled isocitrate lyase was subjected to alkaline hydrolysis, mixed with chemically synthesized phosphohistidine standards, and analyzed by anion exchange chromatography [7].
• In addition, loss of catalytic activity after treatment with potato acid phosphatase indicates that catalytically active isocitrate lyase is the phosphorylated form of the enzyme [7].

Chemical compound and disease context of aceA

• Phosphoenolpyruvate inhibited Escherichia coli NADP-isocitrate dehydrogenase allosterically (Ki of 0.31 mM) and isocitrate lyase uncompetitively (Ki' of 0.893 mM) [8].
• The phosphorylation of NADP-specific isocitrate dehydrogenase in an isocitrate lyase and in a malate synthase mutant of Escherichia coli has been investigated [9].
• Alkylation of isocitrate lyase from Escherichia coli by 3-bromopyruvate [10].

Biological context of aceA

• DNA sequence analysis of the cloned gene and N-terminal protein sequencing of the cloned and wild-type enzymes revealed an entire aceA gene which encodes a 429-amino-acid residue polypeptide whose C-terminus is histidine [1].
• Isocitrate lyase and malate synthase were readily identified by autoradiography after the products of the operon clone were labeled by the maxicell procedure and then resolved by electrophoresis [11].
• Moreover, the main metabolic pathways and carbon flow operating during cell biotransformation was that controlled by the ICDH/ICL ratio, which decreased from 8.0 to 2.5, and the phosphotransferase/ACS ratio, which increased from 2.1 to 5.2, after a NaCl pulse fivefold the steady-state level [12].
• The fully sequenced open reading frame encodes 436 amino acids with a deduced M(r) of 47.5 kDa, consistent with the observed M(r) (49-67.5 kDa) of most ICL enzymes reported so far [2].
• Downstream of aceA, a gene essential for thiamine biosynthesis was identified [13].

Anatomical context of aceA

• The M. tuberculosis model reproduced the observation that deletion of one of the two isocitrate lyase genes has little effect on bacterial growth in macrophages, but deletion of both genes leads to the elimination of the bacilli from the lungs [14].

Associations of aceA with chemical compounds

• Therefore it seems unlikely that the glyoxylate cycle serves primarily a gluconeogenic role in starved (detached) cotyledons, in contrast to post-germinative and senescing cotyledons where PCK, ICL and MS are coordinately synthesised [15].
• While exogenous sucrose greatly represses expression of icl and ms genes in dark-incubated cotyledons, it has a smaller effect on the level of PCK mRNA [15].
• Itaconate, a succinate analog which inhibited both forms of isocitrate lyase in crude extracts, did not affect the growth of Y. pestis under conditions where little isocitrate lyase activity was detected [3].
• Only marginal similarity was observed between this open reading frame (ORF) (termed icl) and a second distinct ORF (named aceA) which exhibits a low similarity to other isocitrate lyases [16].
• Overexpression of aceA in C. glutamicum resulted in specific activities of 0.1 and 7.4 U/mg of protein in minimal medium containing glucose and acetate, respectively [13].

Regulatory relationships of aceA

• Transcriptional analysis revealed that aceA and aceB are expressed as a 5-kb polycistronic transcript from a promoter upstream of aceA [17].

Other interactions of aceA

• This structure, which masks the ribosome-binding site and start codon for aceK, may contribute to the downshift in expression observed between aceA and aceK [18].
• A second gene, aceA, which is likely to encode the E1 component of PDH, was identified upstream from aceB [17].
• Mutants of Escherichia coli K-12 constitutive for the synthesis of the enzymes of fatty acid degradation (fadR) have elevated levels of the glyoxylate shunt enzymes, isocitrate lyase and malate synthase [19].
• The data also showed that only iclR mutation strains exhibited isocitrate lyase and malate synthase activities [20].

Analytical, diagnostic and therapeutic context of aceA

• Fluorimetry and c.d. in both the near- and the far-u.v. regions showed no differences between the mutants and wild-type ICL, indicating that the conformations of the three enzymes were very similar [21].
• Site-directed mutagenesis of cysteine-195 in isocitrate lyase from Escherichia coli ML308 [21].
• Reversed phase HPLC revealed the absence of detectable isocitrate lyase activity in guinea pig, rat and chick embryonic liver [22].
• Diethylpyrocarbonate also reacted with sulphydryl groups in isocitrate lyase, as judged by titrations with Nbs2, but this reaction was not responsible for the failure of hydroxylamine to reactivate the enzyme fully [23].
• Purification of isocitrate lyase from Escherichia coli and watermelon using fast protein liquid chromatography [24].

References