A gene sequence construct used for the treatment of central nervous system diseases: by means of the construction of an auto-processing expression vector, tyrosine hydroxylase (TH), GTP-cyclohydrolase I (GCH1), aromatic amino acid dopa decarboxylase (AADC), and so on may be simultaneously expressed; proteins are connected by means of an auto-processing unit (APU); the use of a viral vector to introduce the construct into a target cell may ultimately result in the high-efficiency expression of tyrosine hydroxylase (TH), GTP-cyclohydrolase I (GCH1), aromatic amino acid dopa decarboxylase (AADC), and so on having independent functions, being used in the prevention or treatment of Parkinson's disease, Alzheimer's disease and other neurodegenerative diseases.

Disclosed herein are methods that may be used for the synthesis of benzylisoquinoline alkaloids (BIAs) such as alkaloid morphinan. The methods disclosed can be used to produce thebaine, oripavine, codeine, morphine, oxycodone, hydrocodone, oxymorphone, hydromorphone, naltrexone, naloxone, hydroxycodeinone, neopinone, and/or buprenorphine. Compositions and organisms useful for the synthesis of BIAs, including thebaine synthesis polypeptides, purine permeases, and polynucleotides encoding the same, are provided.