Question

What are the consequences of deficiencies of the acyl-CoA dehydrogenase enzyme? Discuss the normal role of the enzyme, and how reduced activity impacts fatty acid metabolism. What metabolites used for fuel do you expect to be higher in the blood? What metabolites used for fuel do you expect to be much lower in the blood? How do the excess or lack of these metabolites influence the function of the organs that deal with these metabolites?

Answer 1

Long-chain 3-hydroxy acyl-coenzyme A dehydrogenase (LCHAD) is 1 of 3 enzymatic activities that make up the trifunctional protein of the inner mitochondrial membrane. The other 2 activities of the protein are 2-enoyl coenzyme A (CoA) hydratase (LCEH) and long-chain 3-ketoacyl CoA thiolase (LCKT). The protein is an octamer composed of 4 alpha subunits that contain the LCEH and long-chain 3-hydroxy acyl-coenzyme A dehydrogenase activities, and 4 beta subunits that contain the LCKT activity. This enzyme complex metabolizes long-chain fatty acids, and the long-chain 3-hydroxy acyl-coenzyme A dehydrogenase activity is specific for compounds of C12-C16 chain length. The genes for the alpha and beta subunits have been localized to chromosome 2.

Affected infants with long-chain 3-hydroxy acyl-coenzyme A dehydrogenase deficiency, which is inherited as an autosomal recessive trait, present in infancy with acute hypoketotic hypoglycemia. These episodes typically appear for the first time after a fast, which usually occurs in the context of intercurrent illness with vomiting.