There are four different types of hexokinase, which are controlled by different genes on different chromosomes. Taking human body as an example, hexokinase I is controlled byChromosome 10The hexokinase II is controlled by the upper geneChromosome 2The hexokinase III is controlled by the gene on theChromosome 5The hexokinase IV is controlled by theChromosome 7Gene control (also known asGlucokinase）。(Note In recent years, researchers have usedgenomeMethods to characterize variousvertebrateSpecies andClose relativesA similar HK gene is found in the hexokinase gene in the. It is named as the hexokinase domain protein 1 (HKDC1) and is considered to be the fifth hexokinase.The HKI and HKDC1 genes are arranged end to end, indicating that they are connected by tandemGene replicationEvent)
staybiochemistryKinases are a class of enzymes that are derived from high-energy donor molecules (such as ATP（Adenosine triphosphate）An enzyme that transfers phosphate groups to specific target molecules (substrates);This process is calledPhosphorylation。
Generally speaking, the purpose of phosphorylation is to "activate" or "energize" the substrate molecule and increase its energy so that it can participate in the subsequentfree energyNegative change reaction.All kinases need a bivalentmetal ion(such as Mg2+or Mn2+), which can stabilize donor moleculesHigh energy bondAnd provide the possibility for the occurrence of phosphorylation.
The largest group of kinases isprotein kinase。Protein kinases act on specificproteinAnd change its activity.These kinases are found in thesignal transduction Extremely complexLife activitiesHas played a wide role.Other different kinases act onSmall moleculeSubstance（lipid, sugaramino acid、nucleosideAnd so on), or to send signals, or make thembiochemical reaction The original meaning of ready "kinase" refers to the enzyme that "excites" the substrate molecule, so it generally refers to the transfer of phosphate group from a nucleoside triphosphate toReceptor moleculeThe receptor molecules are activated (become more unstable) by obtaining energy through the transfer of this phosphate group, so many kinases need to transfer phosphate groups from NTP, but as Jensen gave an example, sometimes kinases can also be activated by AMP andinorganpyrophosphateTransfer phosphate group, although generally, AMP and pyrophosphate cannot be calledHigh-energy compound, but "high energy" and“low-energy”It is relative. There is no absolute standardphosphorylaseCompared with the use of inorganic phosphoric acid as phosphate group donor, AMP and pyrophosphoric acid are obviously "high-energy".
Reaction process
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For catalysisHexose6 bits up fromATPAn enzyme that causes phosphorylation.EC 2．7．1．1。hisReaction processYes:
Hexose ATP → Hexose-6-phosphate ADP
yesα－DglucoseOfAffinityIt is very high (Km=1 × 10-5M), and other hexoses can also be phosphorylated.The balance of this reaction shifts to the right.△ G ° '=4.0 kcal.The enzyme is widely found in cells that use sugar as energy, but most of them are in yeast, liver, muscle, brain, etc.The enzyme can be crystallized.The molecular weight is about 96 thousand (yeast hexokinase).It can be activated by Mg2 and K, but can be inhibited by HS reagent.The hexokinase of animals acts asIsoenzymeAnd exist.
