Here I have links to structures of a number of enzymes which are involved in the production of the aromatic amino acid derived alkaloids in some fashion. If you are unfamiliar with protien viewing, I have also created a number of links where PDB files and viewers may be downloaded. Structure Downloads and Some Information About the Enzymes
RasMol ViewerA Molecular Graphics Visualization Tool
MolW PDB ViewerA nice program for viewing protein structures, a list of the amino acid composition of the protein is available while viewing the structures, allowing for individual residues to be pinpointed. This one is nice for looking at enzyme mechanisms and looking at active site conformations.
WebLab Viewer and Viewer LiteI personally found this program to have easier to look at graphics compared to MolW PDB viewer, but it does not have the applications that MolW Viewer has (at least in the lite version). Nonetheless, an excellent program, especially if you are more interested in overall topology or schematics, which this program displays very well.
RCSB Coordinate Database This is where you can find one of the most accesible and largest databases of coordinates for protein structures.