L34: FA Oxidation and Ketogenesis

Question 1

fatty acyl-CoA synthetase

Answer 1

Once in the cell, fatty acids are activated via fatty acyl-CoA synthetase (a.k.a. thiokinase) in the cytosol by attaching CoA to form fatty acyl CoA. Only activated fatty acids (fatty acyl CoA) are used in metabolism.

Question 2

Regulation of Carnitine Shuttle

Answer 2

Malonyl CoA is an allosteric inhibitor of carnitine
acyltransferase I (CPTI) in the FED state. Malonyl CoA is produced during FA synthesis by the action of acetyl-CoA carboxylase. Since malonyl CoA inhibits transport of FA into the mitochondria, this ensures that any newly synthesized fatty acids remain in the cytosol and are not immediately oxidized in the fed state.