Classes
There are two principal classes of fatty acid synthases.
- Type I systems utilise a single large, multifunctional polypeptide and are common to both mammals and fungi (although the structural arrangement of fungal and mammalian synthases differ). A Type I fatty acid synthase system is also found in the CMN group of bacteria (corynebacteria, mycobacteria, and nocardia). In these bacteria, the FAS I system produces palmititic acid, and cooperates with the FAS II system to produce a greater diversity of lipid products.
- Type II is found in archaeabacterial and eubacterial, and is characterized by the use of discrete, monofunctional enzymes for fatty acid synthesis. Inhibitors of this pathway (FASII) are being investigated as possible antibiotics.
The mechanism of FAS I and FAS II elongation and reduction is the same, as the domains of the FAS II enzymes are largely homologous to their domain counterparts in FAS I multienzyme polypeptides. However, the differences in the organization of the enzymes - integrated in FAS I, discrete in FAS II - gives rise to many important biochemical differences.
The evolutionary history of fatty acid synthases are very much intertwined with that of polyketide synthases (PKS). Polyketide synthases use a similar mechanism and homologous domains to produce secondary metabolite lipids. Furthermore, polyketide synthases also exhibit a Type I and Type II organization. FAS I in animals is thought to have arisen through modification of PKS I in fungi, whereas FAS I in fungi and the CMN group of bacteria seem to have arisen separately through the fusion of FAS II genes.
Read more about this topic: Fatty Acid Synthase
Famous quotes containing the word classes:
“My plan of instruction is extremely simple and limited. They learn, on week-days, such coarse works as may fit them for servants. I allow of no writing for the poor. My object is not to make fanatics, but to train up the lower classes in habits of industry and piety.”
—Hannah More (1745–1833)
“Between richer and poorer classes in a free country a mutually respecting antagonism is much healthier than pity on the one hand and dependence on the other, as is, perhaps, the next best thing to fraternal feeling.”
—Charles Horton Cooley (1864–1929)
“... too much attention is paid to dress by those who have neither the excuse of ample means nor of social claims.... The injury done by this state of things to the morals and the manners of our lower classes is incalculable.”
—Mrs. H. O. Ward (1824–1899)