 L-DOPA is converted to dopamine in the brain and various parts of the body by the enzyme DOPA decarboxylase.L-DOPA is used rather than dopamine itself because, unlike dopamine, it is capable of crossing the blood-brain barrier.It is often co-administered with an enzyme inhibitor of peripheral decarboxylation such as carbidopa or benserazide, to reduce the amount converted to dopamine in the periphery and thereby increase the amount of L-DOPA that enters the brain.