Activity of the bacterial enzyme acetoacetate decarboxylase sharply declines below ph 6, suggesting there is an ionizable catalytic residue with pka ~ 6. using mutagenesis, this critical catalytic residue was determined to be lys-115. a) what is the typical pka of a lysine side chain and what ratio of deprotonated to protonated lysine would be expected at ph 7.5 (standard ph inside a bacterium)

Explanation:

From literature, we know that the typical pka of a lysine side is 10.3.

Then we use the Henderson-Hasselbalch equation:

In this case, [A⁻] is the concentration of deprotonated lysine, and [HA] is the concentration of protonated lysine.

We put the data from the problem in the equation and calculate the ratio of deprotonated to protonated lysine:

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