Evidence for the participation of biotin in the enzymic synthesis of fatty acids

Wakil, Salih J.; Titchener, Edward Bradford; Gibson, D. M.

doi:10.1016/0006-3002(58)90177-x

Cited by 265 publications

(52 citation statements)

References 7 publications

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“…This inhibition can be completely reversed by additions of biotin to the reaction mixture. The fact that acetate incorporation into fatty acids is inhibited by avidin indicates the involvement of a biotin enzyme (11,23). This suggests that the fatty acid sy-stem from developing soybean cotvledons synthesizes fatty acids from acetate vzia malonviCoA or de novo, and not bv chain elongation.…”

Section: Resultsmentioning

confidence: 99%

Biosynthesis of Fatty Acids by a Soluble Extract From Developing Soybean Cotyledons

Rinne

1969

Plant Physiol.

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A bstract. Fractionation of developing soybean cotyledons into cellular components demonstrates that most of the activity necessary to incorporate acetate-i-1] C into lipid remains in the supernatant from a 198,000g spin for 1 hr. The system studied is dependent upon ATP, CoA, and CO. Concentrations of ATP greater than 4 X 1-3 M are inhibitory, while 1 X 10-4 M CoA is needed for optimal activity. Avidin inhibition of acetate incorporation into lipid could be reversed by biotin. Studies indicated that NADPH is a better source of reducing power than NADH. The system studied is inhibited by p-chloromercuribenzoic acid and this inhibition can be reversed by an excess of GSH. The system studied shows maximum activity in tris buffer at pH 8.6 or in glycine buffer, pH 9.4. Plants were grown in gravel cuiltul-e (2) tinder a 14 hr photoperiod in the greenihouse. The sovbeanis were removed from the l)ods alld the seed coats.plumule, hypocotyl. and radicle were removed fromll the cotvledons. The cotyledonls were placed in distilled water at room temperatuire unltil grinding. About 10 g of soybean cotyledons were ground with 20 ml of '0.5 M sucrose + 0.01 M MES [2-(N-morpholino)ethanesulfonic acid], pH 6.1. at room temperature. The slurry was passed through 8 layers of cheesecloth and the homogenate was considered the crude enzyme. The crude enzvme was spun at 21,600g for 20 min at 100. The supernatant was then spun at 198,000g for 60 min at 10°. Protein was determined by the biuret method.Assay Method. The reaction was carried out in a 25 ml Erlenmever flask at the temperature and for the time specified. The reaction was stopped with 15 % ethanolic KOH followed by saponification for 3 to 4 hr at 500. After saponification, the 89 www.plantphysiol.org on May 12, 2018 -Published by Downloaded from

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Section: Resultsmentioning

confidence: 99%

Biosynthesis of Fatty Acids by a Soluble Extract From Developing Soybean Cotyledons

Rinne

1969

Plant Physiol.

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“…4 Ten years later the pioneering efforts of Salih Wakil demonstrated that biotin was covalently attached to acetyl-CoA carboxylase thus proving it to be an essential cofactor for enzyme catalysis. 5 It is now well established that the primary biological role of biotin is to serve as an enzymic cofactor required for the transfer of carbon dioxide.…”

Section: Introductionmentioning

confidence: 99%

The enzymes of biotin dependent CO₂ metabolism: What structures reveal about their reaction mechanisms

2012

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Biotin is the major cofactor involved in carbon dioxide metabolism. Indeed, biotindependent enzymes are ubiquitous in nature and are involved in a myriad of metabolic processes including fatty acid synthesis and gluconeogenesis. The cofactor, itself, is composed of a ureido ring, a tetrahydrothiophene ring, and a valeric acid side chain. It is the ureido ring that functions as the CO 2 carrier. A complete understanding of biotin-dependent enzymes is critically important for translational research in light of the fact that some of these enzymes serve as targets for antiobesity agents, antibiotics, and herbicides. Prior to 1990, however, there was a dearth of information regarding the molecular architectures of biotin-dependent enzymes. In recent years there has been an explosion in the number of three-dimensional structures reported for these proteins. Here we review our current understanding of the structures and functions of biotindependent enzymes. In addition, we provide a critical analysis of what these structures have and have not revealed about biotin-dependent catalysis.

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“…ACC1 was isolated and characterized by Wakil et al (6) and functions to carboxylate acetyl-CoA to form malonyl-CoA. Subsequently, a second ACC isoform, ACC2, was identified in mammals that is encoded by a separate gene but carries out the same enzymatic reaction (7,8).…”

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confidence: 99%

Induced polymerization of mammalian acetyl-CoA carboxylase by MIG12 provides a tertiary level of regulation of fatty acid synthesis

Kim

Moon

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

126

137

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Acetyl-CoA carboxylase (ACC), the first committed enzyme in fatty acid (FA) synthesis, is regulated by phosphorylation/dephosphorylation, transcription, and an unusual mechanism of protein polymerization. Polymerization of ACC increases enzymatic activity and is induced in vitro by supraphysiological concentrations of citrate (>5 mM). Here, we show that MIG12, a 22 kDa cytosolic protein of previously unknown function, binds to ACC and lowers the threshold for citrate activation into the physiological range (<1 mM). In vitro, recombinant MIG12 induced polymerization of ACC (as determined by nondenaturing gels, FPLC, and electron microscopy) and increased ACC activity by >50-fold in the presence of 1 mM citrate. In vivo, overexpression of MIG12 in liver induced ACC polymerization, increased FA synthesis, and produced triglyceride accumulation and fatty liver. Thus, in addition to its regulation by phosphorylation and transcription, ACC is regulated at a tertiary level by MIG12, which facilitates ACC polymerization and enhances enzymatic activity.lipogenesis | SREBPs | steatosis F atty acids (FAs) are the essential components of phospholipids and provide the most important energy depot for the body in the form of triglycerides (TG). Newly synthesized FAs also serve as signaling molecules and modulators of transcription factor activity (1-3). Excess accumulation of FAs in tissues contributes to the pathogenesis of many common diseases, including insulin resistance, nonalcoholic fatty liver disease, diabetes, and cancer (4, 5). Given the central role of FAs in these diseases, the enzymes of FA biosynthesis are potential therapeutic targets.The first committed step in FA biosynthesis is carried out by acetyl-CoA carboxylase (ACC). ACC1 was isolated and characterized by Wakil et al. (6) and functions to carboxylate acetyl-CoA to form malonyl-CoA. Subsequently, a second ACC isoform, ACC2, was identified in mammals that is encoded by a separate gene but carries out the same enzymatic reaction (7,8).ACCs are members of a larger family of carboxylases that require biotin and ATP and use bicarbonate as a carbon donor. The malonyl-CoA produced by ACC can be used by FA synthase (FAS) for the sequential 2-carbon elongation reactions that generate palmitic acid (C16:0) in the cytosol. While both ACC1 and ACC2 produce malonyl-CoA, ACC1 is predominantly cytosolic and generates malonyl-CoA that is used by FAS to synthesize palmitic acid. ACC2 is associated with the mitochondrial membrane (9) and produces malonyl-CoA that serves to allosterically inhibit carnitine palmitoyl transferase I, the protein responsible for transport of long chain FAs into mitochondria for β-oxidation (10).Regulation of ACC1 and ACC2 occurs at multiple levels. ACC activity is acutely regulated by phosphorylation/dephosphorylation. AMP-activated protein kinase phosphorylates ACC and inhibits enzyme activity (11). In the fed state, excess glucose must be converted to FAs for energy storage in the form of TGs. Increased insulin signaling in the fed state res...

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Evidence for the participation of biotin in the enzymic synthesis of fatty acids

Cited by 265 publications

References 7 publications

Biosynthesis of Fatty Acids by a Soluble Extract From Developing Soybean Cotyledons

Biosynthesis of Fatty Acids by a Soluble Extract From Developing Soybean Cotyledons

The enzymes of biotin dependent CO₂ metabolism: What structures reveal about their reaction mechanisms

Induced polymerization of mammalian acetyl-CoA carboxylase by MIG12 provides a tertiary level of regulation of fatty acid synthesis

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Evidence for the participation of biotin in the enzymic synthesis of fatty acids

Cited by 265 publications

References 7 publications

Biosynthesis of Fatty Acids by a Soluble Extract From Developing Soybean Cotyledons

Biosynthesis of Fatty Acids by a Soluble Extract From Developing Soybean Cotyledons

The enzymes of biotin dependent CO2 metabolism: What structures reveal about their reaction mechanisms

Induced polymerization of mammalian acetyl-CoA carboxylase by MIG12 provides a tertiary level of regulation of fatty acid synthesis

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The enzymes of biotin dependent CO₂ metabolism: What structures reveal about their reaction mechanisms