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QuickView for Phosphofructokinase, conserved site (biogroup)
- Description:
- The enzyme-catalysed transfer of a phosphoryl group from ATP is animportant reaction in a wide variety of biological processes. Oneenzyme that utilises this reaction is phosphofructokinase (PFK), whichcatalyses the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate, a key regulatory step in the glycolytic pathway. PFK exists as a homotetramer in bacteria and mammals (where each monomerpossesses 2 similar domains), and as an octomer in yeast (where there are4 alpha- (PFK1) and 4 beta-chains (PFK2), the latter, like the mammalianmonomers, possessing 2 similar domains). PFK is ~300 amino acids in length, and structural studies of thebacterial enzyme have shown it comprises two similar (alpha/beta) lobes: one involved inATP binding and the other housing both the substrate-binding site and the allosteric site (a regulatory binding site distinct from the active site, but that affects enzymeactivity). The identical tetramer subunits adopt 2 different conformations: in a 'closed' state, the bound magnesium ionbridges the phosphoryl groups of the enzyme products (ADP and fructose-1,6-bisphosphate); and in an 'open' state, the magnesium ion binds only the ADP, as the 2 products are now further apart. These conformations arethought to be successive stages of a reaction pathway that requires subunitclosure to bring the 2 molecules sufficiently close to react.Deficiency in PFK leads to glycogenosis type VII (Tauri's disease), anautosomal recessive disorder characterised by severe nausea, vomiting,muscle cramps and myoglobinuria in response to bursts of intense orvigorous exercise. Sufferers are usually able to lead a reasonablyordinary life by learning to adjust activity levels.This entry represents a region located in the C terminus that contains three basic residues involved in fructose-6-phosphate binding.
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