Firefly luciferase is the enzyme that allows fireflies to illuminate their abdom

Question

Firefly luciferase is the enzyme that allows fireflies to illuminate their abdomens. Because this light generation is an ATP-requiring reaction, firefly luciferase can be used to test for the presence of ATP. In this way, luciferase can test for the presence of life. The coupled reactions are

luciferin+O2ATP??oxyluciferin+lightAMP+PPi

If the overall ?G of the coupled reaction is -5.60kJ/mol , what is the equilibrium constant, K, of the first reactions at 19?C ? The ?Gfor the hydrolysis of ATP to AMP is ?31.6 kJ/mol.

Explanation / Answer

?Go=?RTlnKeq

Overall ?G = -5.60 kJ/mol

?G for hydrolysis of ATP to AMP = -31.6 kJ/mol.

lucefirin +O2-->Oxylucefirin + light is the reaction for which we need to calculate equilibrium constant, K

?Gfor lucefirin oxidation=-5.60 kJ/mol -(-31.6 kJ/mol).=26kJ/mol

?Go=?RTlnKeq

lnKeq=?Go/RT

  lnKeq =26kJ/mol/-0.008314KJ/mol Kx292K

lnKeq=-10.7097

Keq=e^-10.7097=1.95^-11

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