Thats great, thanks alot. I can indeed retrieve imformation about the genes coding for the proteins that lack mapping in the gene2refseq table. But of course for 160514 protein IDs it might take quite a while to retrieve all the information that way. That is why I was hoping there is a version of the gene2refseq table which includes all updated or removed proteins or if there are archives of previous gene2refseq tables.
It seems a part of the protein IDs are just updated instead of deleted and I might be able to map them by removing the version identifier. That might reduce the number of unmapped protein IDs by a lot and if noone else has an idea how to map deleted protein IDs in a fast manner, I will try your approach. Again thanks alot.
Post a few examples of ID's you are not able to find.
Here is a random sample of OrthoDB entries whose protein IDs don't have any entry in the gene2refseq table. From 3847929 mammalian genes in the OrthoDB database this applies to 160514 genes but only from 38 species (see below the genes)