MyCompoundID MS/MS Search: Metabolite Identification Using a Library of Predicted Fragment-Ion-Spectra of 383,830 Possible Human Metabolites

We report an analytical tool to facilitate
metabolite identification
based on an MS/MS spectral match of an unknown to a library of predicted
MS/MS spectra of possible human metabolites. To construct the spectral
library, the known endogenous human metabolites in the Human Metabolome
Database (HMDB) (8,021 metabolites) and their predicted metabolic
products via one metabolic reaction in the Evidence-based Metabolome
Library (EML) (375,809 predicted metabolites) were subjected to in silico fragmentation to produce the predicted MS/MS spectra.
This spectral library is hosted at the public MCID Web site (www.MyCompoundID.org), and a spectral search program, MCID
MS/MS, has been developed to allow a user to search one or a batch
of experimental MS/MS spectra against the library spectra for possible
match(s). Using MS/MS spectra generated from standard metabolites
and a human urine sample, we demonstrate that this tool is very useful
for putative metabolite identification. It allows a user to narrow
down many possible structures initially found by using an accurate
mass search of an unknown metabolite to only one or a few candidates,
thereby saving time and effort in selecting or synthesizing metabolite
standard(s) for eventual positive metabolite identification.