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From Proteopedia

Hexokinase (Glucokinase)

, also known as , is an enzyme that facilitates the phosphorylation of glucose to glucose-6-phosphate in the first step of glycolysis. Glycolysis is the process by which cells break down a molecule of glucose to release energy which can then be used for various cellular processes. Hexokinase is unique in that it functions in both aerobic and anaerobic conditions for glycolysis. In the image to the right, the helices are shown in a brown, while the sheets are a green color. The other colored space filling model in the image is a glucose molecule, which is the ligand in this enzyme catalyzed reaction.(This enzyme is super fabulous!)

Hexokinase with the glucose, at the brown sites, while the gray, purple, and red atoms and molecules represent the ligand. The specific that interacts with the glucose, holds the molecule in the proper position so that proper site is phosphorylated, resulting in glucose-6-phosphate. The specific residue is residue 205, which is an aspartic acid residue, interacts with the alcohol group off the 6-carbon on the glucose molecule.

Hexokinase has many which are used to hold different parts of the protein together. (unfortunately, the link often doesn't work so I am unable to describe how they affect the protein structure specifically.) Hydrogen bonding in the beta sheets can determine if the sheets are parallel or antiparallel. A parallel sheet will have hydrogen bonds that are not formed at right angles to the sheet, while in an antiparallel sheet, the bonds will be about perpendicular to the sheets. Disulfide bonds are not seen in hexokinase because the protein is an intercellular protein, and the intercellular environment is reducing, meaning that most disulfide bonds will be reduced inside the cell.

, colored lime green, are mostly found inside the protein, while the , shown in navy blue, are mostly found on the outside of the protein. This is due to the interaction of the protein with the intercellular molecules, shown as light blue spheres, which push hydrophobic residues into the center of the protein by the hydrophobic effect, while making hydrogen bonds with the polar residues on the outside, which can be seen due to the presence of water only on the outside of the enzyme. When looking at an image of both the , a sort of cage effect can be seen, as the dark blue hydrophilic residues encapsulate the lime green hydrophobic residues.