The dopamine used by your neurons is generated mostly from tyrosine, one of the 20 main amino acids of which proteins are made.  Every protein-containing food you consume contains some amount of tyrosine.  It can also be synthesized within your body from another amino acid, phenylalanine.

This is tyrosine

This is tyrosine.

and this is dopamine

This is dopamine.

See the resemblence?  Your body can turn tyrosine into dopamine in two steps.  First, an enzyme called tyrosine hydroxylase adds two atoms (OH, which is called a ‘hydroxyl’ group) onto tyrosine, turning it into L-DOPA.

L-DOPA is also an amino acid, but not one of the 20 main amino acids comprising proteins.  It is also known as levodopa, the main treatment for Parkinson’s disease (often as part of a combination drug like sinemet).  Much more more on that to come.  Finally, L-DOPA is converted into dopamine by a second enzyme which ‘decarboxylates’ it, meaning that it removes one carbon and two oxygens, in the form of carbon dioxide.