The BioCyc  ontology contains data on metabolic pathways.
Statistics can now be found in the footers of each table in the GREAT web output.
All ontology data was downloaded and built between Oct 14, 2011 and Feb 18, 2012.
GREAT v1.8 BioCyc Pathway statistics are available here.
GREAT v1.2 BioCyc Pathway statistics are available here.
Caspi, R., et al. The MetaCyc Database of metabolic pathways and enzymes and the BioCyc collection of Pathway/Genome Databases, Nucleic Acids Res. 2008 Jan;36(Database issue):D623-31.