Synthesis of Fatty Acids Longer than 16 Carbons?

Question

I understand that the human body when performing Fatty Acid Synthesis can synthesize only until C16 (palmitate). However the ER has desaturases and elongases. I know that desaturases are used to add double bonds, but do humans have elongases to add even more Carbons to a double bond? If so, then this would mean that the human body can synthesize fats longer than C16? Lets take a hypothetical case and say that humans have both desaturases and elongases. Would it be feasible to add double bonds to palmitate via desaturases, then add more carbons to the chain via elongases and then add more double bonds via desaturases? This way, the resulting fatty acid will have an increased length and more unsaturated character (i.e. more double bonds than the prescribed 4 that humans can add at positions 4, 5, 6, and 9)?

Answer 1

Theoretically, this is possible. However, biologically, it is not. Let me explain.

The enzymes desaturases and elongases could theoretically work as you prescribed to make the fatty acids longer. I do not have exact resources to verify this but I am confident to stay that this has been completed in someone's research lab.

However, biologically, this would not be sound. The human body is a complex system with everything from proteins to organelles having a specific function that is "checked" by other molecules. The 16-carbon fatty acid has a specific function due to it being 16 carbons. If more carbons are added to the molecule, it would incompatible for its biological function. Therefore, fatty acids with only 16 carbons are used.