The paper; ‘Structural Basis for the bifunctionality of
fructose-1,6-bisphosphate aldolase phosphatase’ was publicated in Nature in
October 2011. It focuses on the fact that enzymes can be bifunctional, meaning they can catalyse two reactions. Most bifunctional enzymes have two catalytic sites which catalyse the seperate reactions, so each reaction is catalysed in a specific active site. However the enzyme fructose-1,6-bisphosphate aldolase phosphatase (FBPA/P), is unusual in the sense that it has only one active site but two chemically distinct reactions are catalysed by the enzyme.
The two reactions which are catalyzed by FBPA/P are as follows:
1) The first reaction is carried out by the FBPA form of the enzyme (fructose-1,6-bisphosphate aldolase). The reaction is reversible and is an adol condensation of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GA3P) to from fructose bisphosphate (FBP).
2) The second reaction is carried out by the FBPase form of the enzyme. The reaction is a dephosphorylation of fructose bisphosphate (FBP) to fructose-6- phosphate.
The paper looks into the mechanism behind each reaction by studying the crystal structures of FBPA/P in its two different forms. By comparing the structures of the aldolase and phosphatase forms of the bifunctional enzyme they were able to discover the conformational changes which occur within the active site via 3 mobile loop regions. This is discussed in further detail here.
