Fatty Acids

Annotations:

• Acetyl CoA carboxylase is allosterically activated by citrate and isocitrate and inhibited by palmitoyl CoA negative feedback.
• Insulin stimulates acetyl CoA carboxylase activity. Glucagon and adrenalin inhibit it by increasing intracellular levels of cAMP. 

1. Formation of malonyl CoA involves covalent binding of CO2 to biotin using ATP hydrolysis.
2. Using the same enzyme, CO2 is then tranferred to acetyl CoA, producing malonyl-CoA

1. Initial condensation involves an acetyl group and a malonyl group.
2. Acetyl group and malonyl group must be transferred from their CoA derivatives to a condensing enzyme and ACP.

   Annotations:

   • Catalysed by acetyl transacetylase (ATP) and malonyl transacetylase (MT)
3. Four reactions - condensation, reduction, dehydration and then another reduction.

Annotations:

• GLUT 4 - Translocated from the Golgi complex to the plasma membrane in the presence of insulin.

1. As glucose runs out, it is directed to the formation of glycerol 3-phosphate and TAG.

1. Provides FA for esterfication with G-3-P inside adipose tissue.

1. Adrenalin act rapidly in promoting lipolysis by stimulating membrane bound adenyl cyclase, thus increasing levels of cAMP
2. Increasing levels of cAMP are responsible for converting inactive HSL into its active phosphorylated form thus promoting lipolysis

   Annotations:

   • cAMP stimulates cAMP-dependent protein kinase (PKa)
   1. Intracellular cAMP levels are reduced through the activity of cAMP dependent phosphodiesterase which is activated by insulin.
3. Glucocorticoids promote lipolysis through a cAMP-independent pathway.
   1. They promote gene transcription and so increase HSL biosynthesis.