title: MUCHA: multiple chemical alignment algorithm to identify building block substructures of orphan secondary metabolites.
abstract: BACKGROUND
  In contrast to the increasing number of the successful genome projects, there still remain many orphan metabolites for which their synthesis processes are unknown. Metabolites, including these orphan metabolites, can be classified into groups that share the same core substructures, originated from the same biosynthetic pathways. It is known that many metabolites are synthesized by adding up building blocks to existing metabolites. Therefore, it is proposed that, for any given group of metabolites, finding the core substructure and the branched substructures can help predict their biosynthetic pathway. There already have been many reports on the multiple graph alignment techniques to find the conserved chemical substructures in relatively small molecules. However, they are optimized for ligand binding and are not suitable for metabolomic studies.
  
  
  RESULTS
  We developed an efficient multiple graph alignment method named as MUCHA (Multiple Chemical Alignment), specialized for finding metabolic building blocks. This method showed the strength in finding metabolic building blocks with preserving the relative positions among the substructures, which is not achieved by simply applying the frequent graph mining techniques. Compared with the combined pairwise alignments, this proposed MUCHA method generally reduced computational costs with improving the quality of the alignment.
  
  
  CONCLUSIONS
  MUCHA successfully find building blocks of secondary metabolites, and has a potential to complement to other existing methods to reconstruct metabolic networks using reaction patterns.
authors.affiliation: Bioinformatics Center, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kotera
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tokimatsu
authors.forename: Minoru
authors.initials: M
authors.lastname: Kanehisa
authors.forename: Susumu
authors.initials: S
authors.lastname: Goto
mesh_terms: D000465:Algorithms; D002621:Chemistry / Q000379:methods*; D053858:Metabolic Networks and Pathways