Question

How is hexokinase regulated within its metabolic pathway (e.g. allosteric, enzyme cascades, protein modification, inhibitor, compartmentalization, etc)? Explain.

Answer 1

Hexokinase is the enzyme that catalyzes this phosphoryl group transfer. Hexokinase undergoes and induced-fit conformational change when it binds to glucose, which ultimately prevents the hydrolysis of ATP. It is also allosterically inhibited by physiological concentrations of its immediate product, glucose-6-phosphate.

Hexokinase, the enzyme catalyzing the first step of glycolysis, is inhibited by its product, glucose 6-phosphate. In turn, the level of glucose 6-phosphate rises because it is in equilibrium with fructose 6-phosphate. Hence, the inhibition of phospho fructokinase leads to the inhibition of hexokinase. Hexokinase is the enzyme that catalyzes this phosphoryl group transfer. Hexokinase undergoes and induced-fit conformational change when it binds to glucose, which ultimately prevents the hydrolysis of ATP. It is also allosterically inhibited by physiological concentrations of its immediate product, glucose-6-phosphate.

Glucokinase (hexokinase D) is a monomeric cytoplasmic enzyme found in the liver and pancreas that serves to regulate glucose levels in these organs. Glucokinase is used in the first step of the metabolism of glucose, during this step the phosphorylation of glucose by ATP generates glucose-6-phosphate and ADP.

Glucokinase is induced by insulin, and defects in glucokinase can caused maturity-onset diabetes of the young (MODY). Hexokinase is found in most tissues. Notably, the enzyme is not induced by insulin, but does undergo negative feedback inhibition by glucose-6-phosphate.