Question

where is the hexokinase enzyme synthesized? in what tissue or cell type? what location in the cell?

Answer 1

[CUT SHORT ANS: Most of the times Hexokinase D (aka Glucokinase) is just refered to as Hexokinase (i found a lot of text in which they did this) so i will answer about Glucokinase as it is the most important hexokinase enzyme.

synthesis location :- hepatocytes (in liver). and  Neuroendocrine cells of the pancreas, gut, and brain.

tissue or cell type ; hepatocytes (in liver) , Beta cells and alpha cells of the pancreatic islets, Glucose-sensitive neurons of the hypothalamus, Enterocytes of the small intestine

cell location : generally in free areas of cytoplasm (near cytoplasmic glucose, so that they can facilitate conversion of glucose into glycogen]

KNOW MORE : * please read the underlined part*

There are four isoenzymes of hexokinase which have different functions but can exist in a single species.

1.) Hexokinase I/A is found in all mammalian tissues, and is considered a "housekeeping enzyme," unaffected by most physiological, hormonal, and metabolic changes.

2. )Hexokinase II/B constitutes the principal regulated isoform in many cell types and is increased in many cancers.It is the hexokinase found in muscle and heart. Hexokinase II is also located at the mitochondria outer membrane so it can have direct access to ATP

3) Hexokinase III/C is substrate-inhibited by glucose at physiologic concentrations. Little is known about the regulatory characteristics of this isoform.

4) Hexokinase IV/D is also known as glucokinase and is described below.

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 a hexokinase isoenzyme. Glucokinase's role in metabolism of glucose can be can be inhibited due to the allosteric properties of glucokinase.It also plays an important role in the regulation of glucose metabolism and because of this regulation glucokinase is a target for drug development in type 2 diabetes.

THE PREDOMINANT CELLS OF THE LIVER ARE THE HEPATOCYTES, AND GLUCOKINASE IS FOUND EXCLUSIVELY IN THESE CELLS.

Most of the glucokinase in a mammal is found in the liver, and glucokinase provides approximately 95% of the hexokinase activity in hepatocytes.