Final answer:
Carbidopa inhibits the enzyme DOPA decarboxylase, increasing the availability of L-DOPA for conversion into dopamine in the brain and easing Parkinson’s disease symptoms.
Step-by-step explanation:
The mechanism of action of carbidopa in the combination agent carbidopa-levodopa, which is used for the treatment of Parkinson's disease, is C. DOPA decarboxylase inhibition. Carbidopa works by inhibiting the enzyme aromatic L-amino acid decarboxylase, also known as DOPA decarboxylase, which is responsible for converting L-DOPA into dopamine outside of the brain. By inhibiting this enzyme, more L-DOPA is available to enter the brain where it can then be converted into dopamine, which is necessary for proper motor function and is deficient in Parkinson's patients.