AIIMS November 2011 – MCQ 106

In a well fed state, carnitine shuttle in outer membrane of mitochondria is inhibited by?
A. Malonyl CoA
B. Acetyl CoA
C. Pyruvate
D. Glucose

Correct answer : A. Malonyl CoA

Malonyl CoA inhibits carnitine palmitoyltransferase I, thus preventing the entry of long chain acyl groups into the mitochondrial matrix. Therefore, when fatty acid synthesis is occuring in the cytosol (as indicated by the presence of malonyl CoA), the newly made palmitate cannot be transferred into the mitochondria and degraded.
Ref: Biochemistry By Richard A. Harvey, Denise R. Ferrier (via google books)