1601352

11809

Liver carnitine palmitoyltransferase I (CPT I), the rate-limiting enzyme of mitochondrial β-oxidation, rapidly loses its activity when hepatocytes are put in culture. 3-Thia fatty acids reactivate the enzyme and can increase its activity 3–4-fold in 5–10 min. Normal fatty acids are also able to stimulate CPT I, but to a limited extent, compared to 3-thia fatty acid. This activation does not affect malonyl-CoA sensitivity. CPT I in hepatocytes from both fasted and fasted-carbohydrate refed rats is inactivated and reactivated to a similar extent. Free dodecylthioacetic acid (DTA) is at least as efficient as DTA-CoA as activator. CPT I activity in isolated mitochondria is not influenced by incubation with DTA, suggesting that the regulation of CPT I depends on an extramitochondrial component(s) in the cell. It is concluded that fatty acids activate pre-existing, inactive CPT I without involvement of gene transcription and independently of malonyl-CoA.

541

Carnitine palmitoyltransferase , Hepatocyte , Fatty acid oxidation , Malonyl-CoA , Thia fatty acid

Studia Iranica

549

549