You are examining cells extracted from a squamous cell tumor of the neck and find that they metabolize palmitic acid at a reduced rate compared to cells isolated from normal tissue in the same region of the neck. Which of the following lipid metabolic enzymes is most likely expressed at reduced levels in the cancer cells relative to normal cells?

Question

Quizplus · Accepted Answer

Serine palmitoyltransferase is involved in the initial step of sphingolipid biosynthesis, which includes the metabolism of palmitic acid. Reduced expression of this enzyme could lead to decreased metabolism of palmitic acid in cancer cells.  The initiation of the synthesis of the sphingoid bases (sphingosine, dihydrosphingosine, and ceramides) takes place via the condensation of palmitoyl-CoA and serine. This reaction is catalyzed by serine palmitoyltransferase (SPT). SPT is the rate-limiting enzyme of the sphingolipid biosynthesis pathway. Reduced activity of SPT would result in reduced synthesis of ceramides. Although decreased ceramide synthase 1 activity is associated with more aggressive types of head and neck cancers, it is SPT that utilizes palmitic acid as a substrate and, thus, reduced SPT activity would be associated with reduced palmitate metabolism in these cells

You Are Examining Cells Extracted from a Squamous Cell Tumor