Hexokinase from Saccharomyces cerevisiae

Research area: Cell Signaling

The hexokinase 1 (HXK1) gene is mapped to the Saccharomyces cerevisiae chromosome VI. HXK1 is ubiquitously expressed in mammalian tissues and is abundant in the brain, erythrocytes, lymphocytes, and fibroblasts.

Hexokinase has been used:

• for digesting glucose for measuring glucose content in the root and stem samples of Quercus velutina
• to treat ADP (adenosine diphosphate) solution along with D-glucose to remove the contaminating ATP (adenosine triphosphate)
• in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer (pH 7.5) for ADP-[13CU]glucose synthesis

Catalyzes the phosphorylation of D-hexose sugars at the C6 position utilizing ATP as a phosphate source.

The rate of phosphorylation varies with different hexoses (pH 7.5, 30 °C).
D-fructose K_M: 0.33 mM
D-glucose K_M: 0.12 mM
D-mannose K_M: 0.05 mM

Yeast hexokinase exists as two similar isoforms, PI and PII (A and B), with isoelectric points of 5.25 and 4, respectively.

Molecular Weight: ~ 54 kDa (monomer)
~110 kDa (dimer)
Optimal pH: 7.5 to 9.0
Extinction Coefficient: E^1% = 8.85 (PI) and 9.47 (PII) at 280 nm

Activators: Hexokinase requires Mg²⁺ ions (K_M = 2.6 mM) for activity. Hexokinase is activated by catecholamines and related compounds.

Inhibitors: sorbose-1-phosphate, polyphosphates, 6-deoxy-6-fluoroglucose, 2-C-hydroxy-methylglucose, xylose, lyxose, and thiol reactive compounds (Hg²⁺ and 4-chloromercuribenzoate)

Hexokinase catalyzes the rate-limiting first step of glycolysis, which involves the phosphorylation of glucose.

Lyophilized powder containing approx. 15% sodium citrate

Reconstitute with water or citrate buffer, pH 7.0. Studies have shown excellent stability during repeated freezing and thawing over a period of at least 30 days.

A mixture of isoenzymes.

One unit will phosphorylate 1.0 μmole of D-glucose per min at pH 7.6 at 25 °C.