Saturated Straight-Chain Fatty Acids
The diagrams presented show how fatty acids are synthesized in microorganisms and list the enzymes found in Escherichia coli. These reactions are performed by fatty acid synthase II (FASII), which in general contain multiple enzymes that act as one complex. FASII is present in prokaryotes, plants, fungi, and parasites, as well as in mitochondria.
In animals, as well as yeast and some fungi, these same reactions occur on fatty acid synthase I (FASI), a large dimeric protein that has all of the enzymatic activities required to create a fatty acid. FASI is less efficient than FASII; however, it allows for the formation of more molecules, including “medium-chain” fatty acids via early chain termination.
Once a 16:0 carbon fatty acid has been formed, it can undergo a number of modifications, in particular by fatty acid synthase III (FASIII), which uses 2 carbon molecules to elongate preformed fatty acids.