Glucose-1,6-bisphosphate Synthase - Metabolic Significance of The Catalyzed Reaction

Metabolic Significance of The Catalyzed Reaction

The main product, glucose-1,6-bisphosphate, appears to have several functions:

1. inhibition of hexokinase, an enzyme used in the first step of glycolysis.

2. activation of phosphofructokinase-1 (PFK-1) and pyruvate kinase, both of which are enzymes involved in activation of the glycolytic pathway.

3. acts as a coenzyme for phosphoglucomutase in glycolysis and gluconeogenesis.

4. acts as a cofactor for phosphopentomutase, which produces D-ribose-5-phosphate. 5. acts as a phosphate donor molecule for unknown nonmetabolic effector proteins.

6. increases in concentration during skeletal muscle contraction.

7. dephosphorylation yields glucose-6-phosphate, which is an important precursor molecule in glycolysis and the pentose phosphate pathway.

Glucose-1,6-bisphosphate is most likely used in correlation with gluconeolysis. The product’s inhibition of hexokinase and activation of PFK-1 and pyruvate kinase is indicative of its role in glycolysis. Glucose-1,6-bisphosphate inhibit hexokinase stopping the production glucose-6-phosphate from D-glucose. Its activation of PFK-1 and pyruvate kinase shows that glycolysis still continues without the production of glucose-6-phosphate from D-glucose. This means that the glucose-6-phosphate needed for glycolysis most likely comes from gluconeolysis.

The reactant glucose-1-phosphate is produced by gluconeolysis. This reactant can also form D-glucose-6-phosphate, which is needed for glycolysis. It can therefore be inferred that it is possible when glucose-1-phosphate is produced, it makes glucose-1,6-bisphosphate (with glucose-1,6-bisophosphate synthase) and glucose-6-phosphate. The glucose-1,6-bisphosphate increase the activity of glycolysis, of which glucose-6-phosphate is a reagent.

In addition, one of the reactants (1,3-bisphosphoglycerate) and one of the products (3-phosphoglycerate) are intermediates in the 'payoff' phase of glycolysis. In other words, two molecules involved with glucose-1,6-bisphosphate synthase are able to be both created and recycled in the glycolytic pathway.

The reactant glucose 1-phosphate is an important precursor molecule in many different pathways, including glycolysis, gluconeogenesis and the pentose phosphate pathway.