Hexokinase from Saccharomyces cerevisiae

A mixture of isoenzymes.

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.

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.

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

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.