This enzyme belongs to the family of isomerases, specifically the phosphotransferases (phosphomutases), which transfer phosphate groups within a molecule.
[1][2] As of late 2007, 6 structures have been solved for this class of enzymes, all by the Herzberg group [1] at the University of Maryland using PEPPM from the blue mussel, Mytilus edulis.
However, more recently, a structure with a sulfopyruvate inhibitor, which is a closer substrate analogue, was solved (1M1B);[4] this study supported instead a dissociative mechanism.
In the active-site closeup (left), several sidechains (cyan) that have been identified as important in catalysis are included as well; the overview (right) illustrates the distinctive helix-swapping fold.
Notably, the configuration is retained at phosphorus, i.e. carbon 3 of PPR adds to the same face of phosphorus from which oxygen 2 of PEP was removed; this would be unlikely for a non-enzyme-catalyzed dissociative mechanism, but since the reactive intermediate interacts strongly with the amino acids and magnesium ions of the active site, it is to be expected in the presence of enzyme catalysis.
Because phosphoenolpyruvate mutase has the unusual ability to form a new carbon-phosphorus bond, it is essential to the synthesis of phosphonates, such as phosphonolipids and the antibiotics fosfomycin and bialaphos.
[1] The enzyme phosphonopyruvate decarboxylase presents a solution to this problem: it catalyzes the very thermodynamically favorable decarboxylation of PPR, and the resulting 2-phosphonoacetaldehyde is then converted into biologically useful phosphonates.
The enzyme carboxyphosphoenolpyruvate phosphonomutase performs a similar reaction, converting P-carboxyphosphoenolpyruvate to phosphinopyruvate and carbon dioxide.