Glucokinase Vs Hexokinase

Glucokinase Vs Hexokinase: In reality, the word “hexokinase” refers to a group of enzymes that phosphorylate six-carbon sugars (such as glucose, fructose, galactose, etc.), whereas “glucokinase” refers to a particular isoform of the enzyme with a lower affinity for substrates.

Sometimes, living can appear pretty simple, especially when you are feeling well, joyful, and perhaps seated on a tropical beach. The cells in your body must constantly spend energy just to keep you alive.

Cellular metabolism is a continuous process that involves the generation and use of energy at all scales, from the macroscopic level of moving your muscles to walk, dance, blink, and swallow to the microscopic level of making neurotransmitters and duplicating genetic material.

What is Cellular Metabolism?


As you are probably aware, the primary source of that energy is the food we consume and the subsequent conversion of that food into usable energy. Cellular metabolism includes the breakdown of dietary molecules, in this case glucose, and is an important catabolic mechanism that allows cells to obtain energy (in the form of ATP, adenosine triphosphate).

Glycolysis, the Krebs Cycle, and the electron transport chain make up the three steps of aerobic metabolism, which takes place in the presence of oxygen.

What Is Glycolysis?

Compared to the electron transport chain, the first of these three processes, glycolysis, only produces a little quantity of ATP (2), but it does result in important products (2 pyruvate), which are utilised for the subsequent generation of ATP within the wider metabolic pathway. The other processes of cellular metabolism take place in the mitochondria, while glycolysis takes place in the cytoplasm.

Like many other chemical reactions, the transformation of glucose must first start with the presence of an enzyme. Hexokinase or glucokinase will catalyse the reaction when glucose is phosphorylated into glucose-6-phosphate, depending on a number of factors.

YassineMrabet/Wikimedia Commons provided the photo.

Glucokinase Vs Hexokinase

Although the header of this subsection could imply that these two complement one another, they are actually highly similar and serve the same purpose. Hexokinase is a general word for a group of enzymes that phosphorylate six-carbon sugars (such as glucose, fructose, galactose, etc.), whereas glucokinase is a particular kind of hexokinase (an isoform) that only phosphorylates glucose and not other six-carbon sugars.

The first reaction of glycolysis is catalysed by both of these enzymes, however they are only employed in certain situations.

Hexokinase

All body tissues where cellular metabolism takes place contain this enzyme, with the exception of the liver and the beta cells in the pancreas. It is active when the amount of accessible glucose is stable or low. In other words, on an organismal level, hexokinase is the primary catalyst for cellular metabolism.

Hexokinase has a relatively high affinity for glucose, which allows the enzymatic activity to proceed even in the presence of a low glucose supply and results in the production of two ATP molecules and glucose-6-phosphate. Hexokinase’s maximum response rate (Vmax) is likewise extremely low, making it unsuitable for the quick synthesis of energy from glucose.

Hexokinase has a control mechanism, an allosteric feedback loop with the reaction’s own product, glucose-6-phosphate, much like any other enzymatic reaction does. This indicates that the enzyme will be inhibited from interacting with or reacting with more substrate molecules once enough glucose has been transformed into glucose-6-phosphate (glucose).

Glucokinase

Hexokinase is an isoform of glucokinase, which has different activation requirements than the latter. Contrary to hexokinase, which is found in all tissues, glucokinase is only found in beta cells in the liver and pancreas and functions as a functional regulation mechanism in the body.

Since glucokinase has a low affinity for glucose, it only becomes active when a cell has an abundance of glucose at its disposal. Hexokinase can manage the enzymatic load if there is only a small amount of glucose present, as would be the case during a fast or period of rest. Because of glucokinase’s high maximal response rate (Vmax), glucose is quickly converted into useable energy. Due to the regulatory mechanism for this particular enzyme, glucokinase becomes active after a substantial meal or an input of carbohydrates.

One of its byproducts, glucose-6-phosphate, controls hexokinase allosterically whereas insulin regulates glucokinase hormonally. In actuality, insulin mostly regulates or stimulates glucokinase. Within an hour of an increase in insulin levels, glucokinase transcription and activity both rise. Triiodothyronine and glucocorticoids are two more hormones and metabolic pathways that can alter glucokinase activity, however the enormous array of other metabolic pathways for glucokinase activity is outside the purview of this article.

Diabetes mellitus can seriously affect the effectiveness of glucokinase and, consequently, the production of energy when glucose levels are high because of the crucial function that insulin plays in the regulation of glucokinase in the liver and pancreas.

Final Thoughts

In the process of glycolysis, a crucial stage in the wider pathway of cellular metabolism, hexokinase and glucokinase are both significant enzymes. These two enzymes operate subconsciously, as is the case with the majority of enzymatic operations, and our body will regulate their activation without our involvement.

These enzymes may seem small and inconsequential, but they are always working for us to prepare us for every action we take.