Final answer:
The correct answer is hexokinase, which initiates glycolysis by phosphorylating glucose and traps it within the cell for further metabolism. Hexokinase isomers are notably overexpressed in tumor cells, facilitating the increased glycolytic rates characteristic of the Warburg effect.
Step-by-step explanation:
In mammals, four isomers of the glycolytic enzyme hexokinase have increased expression in tumor cells. During glycolysis, the enzyme hexokinase (or glucokinase in the liver) initiates the metabolic pathway by phosphorylating glucose, which is then trapped within the cell, facilitating further metabolic processes.
Tumor cells exhibit increased expression of hexokinase isomers, which is thought to contribute to the enhanced glucose uptake and glycolytic rates observed in cancer cells, known as the Warburg effect. Hexokinase has a high affinity for glucose and converts it into glucose-6-phosphate, the substrate for the glycolytic pathway.
In tissues such as the liver, glucokinase serves a similar role but is active when blood glucose levels are high. The importance of hexokinase in rapidly metabolizing glucose makes it a key regulatory point in cellular energy production, especially in proliferating tumor cells.