levodopa, or -dopa is an amino acid. in the body of mammals, it is made from tyrosine in a process named synthesis. it also occurs in different plants. as such it can be used as a dietary supplement. l-dopa is the precursor to the neurotransmitters dopamine, norepiphedrine and epiphedrine, which are part of a group known as catecholamines. l-dopa can also be used as a drug for diseases such as parkinson's disease. the substance used in the drug is usually called "levodopa", and the naturally occurring substance is called "l-dopa".