Sirtuins are NAD(+)-dependent protein deacetylases. They mediate adaptive responses to a variety of stresses, including calorie restriction and metabolic stress. Sirtuin 3 (SIRT3) is localized in the mitochondrial matrix, where it regulates the acetylation levels of metabolic enzymes, including acetyl coenzyme A synthetase 2 (refs 1, 2). Mice lacking both Sirt3 alleles appear phenotypically normal under basal conditions, but show marked hyperacetylation of several mitochondrial proteins. Here we report that SIRT3 expression is upregulated during fasting in liver and brown adipose tissues. During fasting, livers from mice lacking SIRT3 had higher levels of fatty-acid oxidation intermediate products and triglycerides, associated with decreased levels of fatty-acid oxidation, compared to livers from wild-type mice. Mass spectrometry of mitochondrial proteins shows that long-chain acyl coenzyme A dehydrogenase (LCAD) is hyperacetylated at lysine 42 in the absence of SIRT3. LCAD is deacetylated in wild-type mice under fasted conditions and by SIRT3 in vitro and in vivo; and hyperacetylation of LCAD reduces its enzymatic activity. Mice lacking SIRT3 exhibit hallmarks of fatty-acid oxidation disorders during fasting, including reduced ATP levels and intolerance to cold exposure. These findings identify acetylation as a novel regulatory mechanism for mitochondrial fatty-acid oxidation and demonstrate that SIRT3 modulates mitochondrial intermediary metabolism and fatty-acid use during fasting.

https://escholarship.org/content/qt74b7b8tf/qt74b7b8tf.pdf?t=qag5yr

SIRT3 regulates mitochondrial fatty-acid oxidation by reversible enzyme deacetylation

Biogenesis of peroxisomes.

http://2010.igem.org/wiki/images/e/e4/Butanol.pdf

Metabolic engineering of Escherichia coli for 1-butanol production.

1-Butanol, an important chemical feedstock and advanced biofuel, is produced by Clostridium species. Various efforts have been made to transfer the clostridial 1-butanol pathway into other microorganisms. However, in contrast to similar compounds, only limited titers of 1-butanol were attained. In this work, we constructed a modified clostridial 1-butanol pathway in Escherichia coli to provide an irreversible reaction catalyzed by trans-enoyl-coenzyme A (CoA) reductase (Ter) and created NADH and acetyl-CoA driving forces to direct the flux. We achieved high-titer (30 g/liter) and high-yield (70 to 88% of the theoretical) production of 1-butanol anaerobically, comparable to or exceeding the levels demonstrated by native producers. Without the NADH and acetyl-CoA driving forces, the Ter reaction alone only achieved about 1/10 the level of production. The engineered host platform also enables the selection of essential enzymes with better catalytic efficiency or expression by anaerobic growth rescue. These results demonstrate the importance of driving forces in the efficient production of nonnative products.

https://www.phys.sinica.edu.tw/TIGP-NANO/Course/2013_Fall/classnote/Seminar_172%20Shen%20AEM%202011.pdf

Driving Forces Enable High-Titer Anaerobic 1-Butanol Synthesis in Escherichia coli

Inhibition of mitochondrial beta-oxidation as a mechanism of hepatotoxicity.

Fluorometric assay of acyl-CoA dehydrogenases in normal and mutant human fibroblasts.

Purification and properties of Escherichia coli coenzyme A-transferase.

The clinical and biochemical phenotype of glutaric acidaemia type II (GAII) has led to the suggestion that the defect in the disorder affects electron transfer from primary FAD-containing dehydrogenases into the respiratory chain. Two proteins are involved in this process, i.e. electron transfer flavoprotein (ETF) and ETF dehydrogenase, an iron—sulphur flavoprotein with a distinctive EPR signal. Reliable catalytic assays for these proteins are not available, but both proteins have been purified and antisera against them prepared in rabbits.

Frank E. Frerman

Papers

Fluorometric assay of acyl-CoA dehydrogenases in normal and mutant human fibroblasts.

Purification and properties of Escherichia coli coenzyme A-transferase.

Glutaric Acidaemia Type II (Multiple Acyl-CoA Dehydrogenation Deficiency)

Molecular and catalytic properties of the acetoacetyl-coenzyme A thiolase of Escherichia coli.

Inhibition of general acyl CoA dehydrogenase by electron transfer flavoprotein semiquinone.