I need to obtain drug-protein interaction data for me website. For example, for aspirin I need to find how strongly it binds to COX1 and whatever other enzymes and proteins it binds to. Or for the MAOI-A gene, I need to get the binding constants for various MAO inhibitors and inducers. I found this site: https://www.bindingdb.org/bind/index.jsp
but their API isn't working so I don't know if I can use it.
You have already found a nice site.
https://www.bindingdb.org/bind/index.jsp
You are right, ChemAxon seems stop working.
See this article:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4702904/
It's a very recent paper,
STITCH 5: augmenting protein–chemical interaction networks with tissue and affinity data
There many of such sites mentioned just below:
https://omictools.com/drug-targets-category
or here:
http://www.drugbank.ca/
or here:
http://dgidb.genome.wustl.edu/getting_started