What is the structure of hexokinase?

What is the structure of hexokinase?

Structure of Hexokinase Hexokinase is composed of an N-terminal regulatory domain and a C-terminal catalytic domain. These two domains are joined together by an alpha helix. The molecular weights of hexokinases are around 100 kD. Each domain weighs about 50kD and contains a glucose binding site.

What is the shape of hexokinase?

Hexokinase is shaped like a clamp, with a big groove in one side (shown in the figure with an arrow). The structure without glucose (PDB entry 2yhx ) is open, allowing access to the active site.

What is the function of hexokinase?

Hexokinase catalyzes the phosphorylation of glucose, the rate-limiting first step of glycolysis. Hexokinase II (HK-II) is a predominant isoform in insulin-sensitive tissues such as heart, skeletal muscle, and adipose tissues.

What is the hexokinase pathway?

Hexokinase (HK), the red cell enzyme with the lowest activity in the glycolytic pathway, catalyzes the initial step in the utilization of glucose and thus is required for both glycolysis and the pentose shunt and produces glucose 6-phosphate.

What class of enzyme is hexokinase?

EnzymeHexokinase / ClassificationEnzymes are proteins that act as biological catalysts. Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Wikipedia

Why is it called hexokinase?

A hexokinase is an enzyme that phosphorylates hexoses (six-carbon sugars), forming hexose phosphate. In most organisms, glucose is the most important substrate for hexokinases, and glucose-6-phosphate is the most important product.

What type of protein is hexokinase?

They can be found in bacteria, plants and vertebrates, including humans. More than one isoform or isozyme can occur in one species, providing different functions. Hexokinases are actin fold proteins and share a common ATP binding site core surrounded by more variable sequences.

Where is hexokinase produced?

Hexokinase IV is present in the liver, pancreas, hypothalamus, small intestine, and perhaps certain other neuroendocrine cells, and plays an important regulatory role in carbohydrate metabolism.

How many amino acids are in hexokinase?

Hexokinase is a large homodimer composed of 920 amino acids in each chain. Since both strands are identical, one one chain will observed . Here is a view of the structure colored from lightest to darkest in the N-terminal to C-terminal direction. The enzyme is made up of many alpha helixes and beta sheets .

Where is the hexokinase located?

Glucokinase (hexokinase D) is a monomeric cytoplasmic enzyme found in the liver and pancreas that serves to regulate glucose levels in these organs.

What is the specific activity of hexokinase II?

The relative specific activity of hexokinase II increases with pH at least in a pH range from 6.9 to 8.5. Hexokinase III/C is substrate-inhibited by glucose at physiologic concentrations. Little is known about the regulatory characteristics of this isoform.

Where does hexokinase come from?

Genes that encode hexokinase have been discovered in every domain of life, and exist among a variety of species that range from bacteria, yeast, and plants to humans and other vertebrates.

What is the size of hexokinase isoforms?

Size of different isoforms. Most bacterial hexokinases are approximately 50 kD in size. Multicellular organisms including plants and animals often have more than one hexokinase isoform.

What is the conformational change of hexokinase?

Hexokinase undergoes an induced fit conformational change when glucose binds. This conformational change prevents the hydrolysis of ATP, and is allosterically inhibited by physiological concentrations of glucose-6-phosphate the product. Hexokinase has two conformational states.