Methapain

http://classyfire.wishartlab.com/tax_nodes/C0000000
http://classyfire.wishartlab.com/tax_nodes/C0002448
http://classyfire.wishartlab.com/tax_nodes/C0002279
http://classyfire.wishartlab.com/tax_nodes/C0000369
http://classyfire.wishartlab.com/tax_nodes/C0000369
http://classyfire.wishartlab.com/tax_nodes/C0003899
http://classyfire.wishartlab.com/tax_nodes/C0001118
http://classyfire.wishartlab.com/tax_nodes/C0002239
http://classyfire.wishartlab.com/tax_nodes/C0004557
http://classyfire.wishartlab.com/tax_nodes/C0003940
http://classyfire.wishartlab.com/tax_nodes/C0004150
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:6807
http://www.hmdb.ca/metabolites/HMDB0014477
http://www.genome.jp/dbget-bin/www_bget?drug:D08195
http://www.genome.jp/dbget-bin/www_bget?cpd:C07163
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=4095
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=46505722
https://www.chemspider.com/Chemical-Structure.3953.html
http://www.bindingdb.org/bind/chemsearch/marvin/MolStructure.jsp?monomerid=82507
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=6813
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=167309
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL651
http://bidd.nus.edu.sg/group/cjttd/ZFTTDDRUG.asp?ID=DAP000267
http://www.pharmgkb.org/drug/PA450401
http://www.rxlist.com/cgi/generic/methdone.htm
https://www.drugs.com/methadone.html
https://en.wikipedia.org/wiki/Methadone