Disease relevance of aceB

• The aceB gene from Corynebacterium glutamicum, encoding malate synthase, was isolated, subcloned and expressed in Escherichia coli and C. glutamicum [1].
• The aceB gene, which encodes malate synthase has been previously cloned from Streptomyces clavuligerus NRRL 3585 and characterized [2].
• A comparison with the sequences of malate synthase from other organisms shows that the phylogenetic distance to the E. coli aceB gene is no closer than that to genes from plants or fungi [3].
• Isocitrate lyase and malate synthase, the two unique enzymes of the glyoxylate cycle, were detected in crude extracts of Yersinia pestis, Y. pseudotuberculosis, and Y. enterocolitica [4].
• Biochemical and structural studies of malate synthase from Mycobacterium tuberculosis [5].

High impact information on aceB

• Gene replacement was further confirmed by the absence of the vector and the 2-kb segment of mas replaced by hyg from the genome of the mutant [6].
• A single gene (mas) encodes the multifunctional enzyme that catalyzes the synthesis of very long chain multiple methyl branched fatty acids called mycocerosic acids that are present only in slow-growing pathogenic mycobacteria and are thought to be important for pathogenesis [6].
• 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 [5].
• In the case of the aceBAK operon, IclR binds to IclR box II between -52 and -19 of the aceB promoter and interferes with binding of the RNA polymerase to this promoter [7].
• A secondary IclR binding site (IclR box I) was identified between -125 and -99 of the aceB promoter [7].

Chemical compound and disease context of aceB

• The aceB-repressing activity of the glxR clone was markedly relieved in an Escherichia coli cya mutant, but the activity was restored in growth medium containing cAMP [8].
• In the present study, we present the 1.95 A-resolution crystal structure of Escherichia coli malate synthase isoform G in complex with magnesium, pyruvate, and acetyl-CoA, and we compare it with previously determined structures of substrate and product complexes [9].
• The phosphorylation of NADP-specific isocitrate dehydrogenase in an isocitrate lyase and in a malate synthase mutant of Escherichia coli has been investigated [10].
• Furthermore, the genomic organisation of the three Streptomyces aceB genes cloned thus far is different from that of other bacterial malate synthases, and warrants further investigation [11].

Biological context of aceB

• Binding of purified GlxR to the promoter region of aceB could be demonstrated only in the presence of cAMP [8].
• The aceB gene has a high G+C content (71.5 mol%), especially in the third codon position [12].
• Malate synthase, an enzyme of the glyoxylate pathway, catalyzes the condensation and subsequent hydrolysis of acetyl-coenzyme A (acetyl-CoA) and glyoxylate to form malate and CoA [9].
• Nucleotide sequence analysis of the respective genomic DNAs, named MS-1 gene and MS-2 gene, revealed that both regions encoding MS had the same length of 1,653 base pairs, corresponding to 551 amino acids (molecular mass of MS-1, 62,448 Da; MS-2, 62,421 Da) [13].
• The glyoxylate pathway was also utilized, as evidenced by the significant upregulation of isocitrate lyase and malate synthase activity in the icd mutant E. coli [14].

Anatomical context of aceB

• Comparison of the sequence of malate synthase from cucumber with that from E. coli and with other glyoxysomal and peroxisomal enzymes, shows that a conserved C-terminal tripeptide is a common feature of those enzymes imported into microbodies [15].

Associations of aceB with chemical compounds

• Glyoxylate enzymes such as aceA and aceB were strongly up-regulated (>10-fold) and TCA-cycle-related enzymes were also up-regulated to some extent [16].
• Oxalate, glycolate and ATP were found to be inhibitors of malate synthase activity [1].
• Malate synthase (EC 4.1.3.2) from dark-grown Euglena gracilis was purified to homogeneity by the criterion of polyacrylamide-gel electrophoresis [17].
• This can explain earlier observations of the susceptibility of the enzyme to inactivation and aggregation upon X-ray irradiation and indicates that cysteine oxidation may play a role in redox regulation of malate synthase activity in vivo [9].
• The diauxic type of growth may be attributed to the failure of cells to form acetyl coenzyme A synthetase and to form isocitrate lyase and malate synthase of the glyoxalate bypass, needed for the assimilation of the produced acetate, until glucose or gluconate has been completely exhausted [18].

Regulatory relationships of aceB

• Transcriptional analysis revealed that aceA and aceB are expressed as a 5-kb polycistronic transcript from a promoter upstream of aceA [19].

Other interactions of aceB

• 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 [20].
• In addition, the differential expression of genes aceB, aceA, and aceK has been tested both in vivo in a minicell system and in vitro in a plasmid-directed transcription-translation coupled system [21].
• Other regulated operons were shown to bind FruR to a single site upstream of the first structural gene as follows: (1) ppsA (positive regulation); (2) icd (positive regulation); (3) aceB (positive regulation); and (4) pts (negative regulation) [22].

Analytical, diagnostic and therapeutic context of aceB

• Malate synthase from Corynebacterium glutamicum: sequence analysis of the gene and biochemical characterization of the enzyme [1].
• The gene, encoding malate synthase (MS), aceB, was cloned from the thermophilic bacterium Streptomyces thermovulgaris by homology-based PCR [23].
• Southern and Western blot analyses showed absence of mas gene and encoded proteins in Mycobacterium smegmatis and Escherichia coli [24].
• Multiple sequence alignment of 26 known malate synthase enzymes revealed that the two proposed sites are highly conserved, despite the low homologies between the two distinct forms of the enzyme (13-18%) [25].

References