<prompt> The only energy-requiring step in fatty acid oxidation is catalyzed by ___ enzyme?ThiokinaseAcyl co A dehydrogenaseThiolaseBeta hydroxy Acyl co A dehydrogenase  <response>: In the presence of ATP and coenzyme A, the enzyme acyl-CoA synthetase thiokinase catalyzes the conversion of a fatty acid to acyl-CoA. Reference: Harpers Illustrated Biochemistry 30th Edition Pg 224 