Sile's Take on Atkins Diet

Fat can be synthesized from other nutrients like carbohydrates. After carbohydrate is converted into acetyl-CoA, it is transferred to the cytosol for fat synthesis (Diwan, 2017).

Steps:

• Biotin, an enzyme prosthetic group, is carboxylized by acetyl-CoA carboxylase with the use of ATP. The carboxyl group is then passed on to acetyl-CoA to produce malonyl-CoA (Diwan, 2017).

• Acetyl-CoA and Malonyl-CoA bind to a fatty acid synthase complex. They both temporarily stay in an ester linkage with a serine hydroxyl group of the complex before getting transferred to a thioester linkage with the phosphopantethiene of the acyl carrier protein domain of the complex.It is catalyzed by malonyl/acetyl-CoA-ACP Transacylase (Diwan, 2017).

• The malonyl component is decarboxylized then the carbonyl carbon of the acyl component is attacked by the resultant carbanion thereby forming a beta ketone. It is catalyzed by the condensing enzyme, beta ketoacyl synthase (Diwan, 2017).

• The beta ketone is reduced to an alcohol by the oxidation of NAD+. It is catalyzed by beta-ketoacyl-ACP reductase (Diwan, 2017). 

• The alcohol is dehydrated and forms a trans double bond. It is catalyzed by beta-hydroxyacyl-ACP dehydratase (Diwan, 2017).

• NADPH reduces the dehydrated alcohol at the trans double bond thereby, making a saturated chain. It is catalyzed by enoyl-ACP reductase (Diwan, 2017).  

• The growing fatty acid is transferred to the cysteine sulfhydryl of a condensing enzyme and the cycle starts again (Diwan, 2017).

• Fatty acid is linked with phosphopantetheine when it is 16 carbon atoms long. This is catalyzed by thioesterase domain. It is catalyzed by malonyl/acetyl-CoA-ACP transacylase (Diwan, 2017).

The 16-C fatty acid is the final product of the complex (Diwan, 2017).

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