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I am currently studying the metabolic pathways for biochemistry and I am not quite clear in which reactions of glycolysis magnesium is involved.

So I have now found out that magnesium is present in the three ATP-dependent reactions (1st, 3rd and 10th reactions), but also in the 2nd, 7th, 8th and 9th steps.

According to this diagram:

glycosis

In our university we have been tought, that Magnesium is present in all ATP reactions, but also in Step 2... this is what causes confusion for me:

enter image description here

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    $\begingroup$ Ok, have you found out what purpose magnesium can have in molecular reactions? $\endgroup$ – Chris♦ Jan 12 at 19:18
  • $\begingroup$ @Chris ok thank you for the hint, i should and will do that now. $\endgroup$ – Alessandro Santamaria Jan 12 at 20:12
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    $\begingroup$ The 'true' substrate for almost all enzymes that use ATP is not free ATP at all but a complex of magnesium and ATP. Any enzyme assay for an ATP-requiring enzyme will include a source of Mg(2+). (Try assaying hexokinase without adding magnesium!). For the problems this can cause in enzyme kinetics, in particular in determining the 'true' substrate concentration, see Concentration of MgATP2- and other ions in solution. Calculation of the true concentrations of species present in mixtures of associating ions $\endgroup$ – user1136 Jan 12 at 21:11
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    $\begingroup$ The general answer to this question is "all reactions involving ATP". This is covered in answers to another question. $\endgroup$ – David Jan 13 at 17:24
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    $\begingroup$ What is the source of your figure with magnesium ions required for the PGI reaction? The paper reporting the crystal structure of PGI and the protopedia page have no involvement of magnesium ions in the mechanism of the reaction. I have no reason, therefore to believe this is true. Furthermore, you should ask your University why they are filling your head with miscellaneous facts (or fictions) instead of teaching you to understand the principles of glycolysis. $\endgroup$ – David Jan 14 at 20:58
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In the 1st step where glucose is converted to glucose-6- phosphate by the enzyme hexokinase, in the 3rd step where fructose-6-phosphate is converted to fructose-1,6-bisphosphate by the enzyme fructose-1,6-bisphosphatase and in the last reaction where 2 phosphoenolpyruvate is converted to pyruvate by the enzyme pyruvate kinase.. In this 3 reaction Magnesium is needed as they are ATP dependent reaction and Magnesium stabilises the ATP in this reaction and help the reactions to proceed faster.

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