The latest release of the UniProt protein database contains just over a billion triples*! PRESS RELEASE :-)
The data is all available via the (Semantic or otherwise) Web: http://beta.uniprot.org/ ...or can be bulk-downloaded from: ftp://ftp.uniprot.org/* Counting some reification statements, and assuming no overlap between "named graphs".
P.S. This should be the last you'll hear from me on this topic -- I'm off to new adventures...