Acetate generation in rat liver mitochondria; acetyl-CoA hydrolase activity is demonstrated by 3-ketoacyl-CoA thiolase.
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Acetate has been found as an endogenous metabolite of beta-oxidation of fatty acids in liver. In order to investigate the regulation of acetate generation in liver mitochondria, we attempted to purify a mitochondrial acetyl-CoA hydrolase in rat liver. This acetyl-CoA-hydrolyzing activity in isolated mitochondria was induced by the treatment of rats with di(2-ehtylhexyl)phthalate (DEHP), a peroxisome proliferator which induces expression of several peroxisomal and mitochondrial enzymes involved in beta-oxidation of fatty acids. The purified enzyme was 43-kDa in molecular mass by SDS/PAGE. Internal amino acid sequencing of this enzyme revealed that it was identical with mitochondrial 3-ketoacyl-CoA thiolase, suggesting that this enzyme has two kinds of activities, 3-ketoacyl-CoA thiolase and acetyl-CoA hydrolase activities. Kinetic studies clearly indicated that this enzyme had the both activities and each activity was inhibited by the substrates of the other activity, that is, 3-ketoacyl-CoA thiolase activity was inhibited by acetyl-CoA, on the other hand, acetyl-CoA hydrolase activity was inhibited by acetoacetyl-CoA in a competitive manner. These findings suggested that acetate generation in liver mitochondria is a side reaction of this known enzyme, 3-ketoacyl-CoA thiolase, and this enzyme may regulate its activities depending on each substrate level. (+info)
Metabolism of acetyl-CoA by isolated peroxisomal fractions: formation of acetate and acetoacetyl-CoA.
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Liver peroxisomal fractions, isolated from rats treated with clofibrate, were shown to hydrolyze added [1-14C]acetyl-CoA to free [1-14C]acetate. [1-14C]Acetyl-CoA was, however, also converted to [14C]acetoacetyl-CoA. This reaction was inhibited by added ATP and by solubilization of the peroxisomes. The effect of ATP on synthesis of [14C]acetoacetyl-CoA was likely due to ATP-dependent stimulation of acetyl-CoA hydrolase (EC 3.1.2.1) activity. The inhibitory effect due to solubilizing conditions of incubation remains unexplained. During peroxisomal beta-oxidation of [1-14C]palmitoyl-CoA, [1-14C]acetyl-CoA, [1-14C]acetate, and [14C]acetoacetyl-CoA were shown to be produced. Possible metabolic implications of peroxisomal acetoacetyl-CoA synthesis are discussed. (+info)
Molecular cloning and functional expression of human cytosolic acetyl-CoA hydrolase.
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A cDNA encoding human cytosolic acetyl-CoA hydrolase (CACH) was isolated from a human liver cDNA library, sequenced and functionally expressed in insect cells. The human CACH cDNA encodes a 555-amino-acid sequence that is 81.4%/78.7% identical to those of the mouse/rat homologue, suggesting a conserved role for this enzyme in the human and rodent livers. Bioinformatical study further reveals a high degree of similarity among the human and rodent CACHs as follows: First, the gene is composed of 15 exons ranging in size from 56 to 157 bp. Second, the protein consists of two thioesterase regions and a C-terminal steroidogenic acute regulatory protein-related lipid transfer (START) domain. Third, the promoter region is GC-rich and contains GC boxes, but lacks both TATA and CCAAT boxes, the typical criteria of housekeeping genes. A consensus peroxisome proliferator responsive element (PPRE) present in the rodent CACH promoter regions supports marked CACH induction in rat liver by peroxisome proliferator (PP). (+info)
Role of acetyl coenzyme A synthesis and breakdown in alternative carbon source utilization in Candida albicans.
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A glucose-repressible gene encodes acetyl-CoA hydrolase from Saccharomyces cerevisiae.
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Acetyl-CoA hydrolase, catalyzing the hydrolysis of acetyl-CoA, is presumably involved in regulating the intracellular acetyl-CoA pool. Recently, a yeast acetyl-CoA hydrolase was purified to homogeneity from Saccharomyces cerevisiae and partially characterized (Lee, F.-J. S., Lin, L.-W., and Smith, J. A. (1989) Eur. J. Biochem. 184, 21-28). In order to study the biological function and regulation of the acetyl-CoA hydrolase, we cloned and sequenced the full length cDNA encoding yeast acetyl-CoA hydrolase. RNA blot analysis indicates that acetyl-CoA hydrolase is encoded by a 2.5-kilobase mRNA. DNA blot analyses of genomic and chromosomal DNA reveal that the gene (so-called ACH1, acetyl-CoA hydrolase) is present as a single copy located on chromosome II. Acetyl-CoA hydrolase is established to be a mannose-containing glycoprotein, which binds concanavalin A. By measuring the levels of ACH1 mRNA and acetyl-CoA hydrolase activity in different growth phases and by examining the effects of various carbon sources, we have demonstrated that ACH1 expression is repressed by glucose. (+info)
ATP synthesis-coupled and -uncoupled acetate production from acetyl-CoA by mitochondrial acetate:succinate CoA-transferase and acetyl-CoA thioesterase in Trypanosoma.
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In vitro cultured human Sertoli cells secrete high amounts of acetate that is stimulated by 17beta-estradiol and suppressed by insulin deprivation.
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