Into the Textbooks It Goes

 
This week's issue of Science contains an important paper.

Maier, T,, Leibundgut, M. and B. Nenad (2008) The Crystal Structure of a Mammalian Fatty Acid Synthase. Science 321:1315-1322.

We've known for a long time that this is a very important enzyme and that it's a classic example of a little protein machine combining the activities of may different enzymes in order to carry out the complex reactions of fatty acid synthesis. Here's how I described it in the last edition of my book ...

In bacteria, each reaction in fatty acid synthesis is catalyzed by a discrete monofunctional enzyme. This type of pathway is known as a type II fatty acid synthesis system (FAS II). In animals, the various enzymatic activities are localized to individual domains in a large multifunctional enzyme and the complex is described as a type I fatty acid synthesis system (FAS I). The large animal polypeptide contains the activities of malonyl/acetyl transferase, 3-ketoacyl-ACP synthase, 3-ketoacyl–ACP reductase, 3-hydroxyacyl–ACP dehydratase, enoyl–ACP reductase, and thioesterase. It also contains a phosphopantetheine prosthetic group (ACP) to which the fatty acid chain is attached. Note that the malonyl CoA:ACP transacylase enzyme shown in Figure 16.3 is replaced by a transferase activity in the FAS I complex. This transferase catalyzes a substrate loading reaction where malonyl CoA is covalently attached to the ACP-like domain on the multienzyme polypeptide chain. The eukaryotic enzyme is called fatty acid synthase.

The structure (shown below) will be going right into the textbooks.

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