MuteinDB: the mutein database linking substrates, products and enzymatic reactions directly with genetic variants of enzymes. - Andreas Braun; Bettina Halwachs; Martina Geier; Katrin Weinhandl; Michael Guggemos; Jan Marienhagen; Anna Joëlle Ruff; Ulrich Schwaneberg; Vincent Rabin; Daniel E. Torres Pazmiño; Gerhard G. Thallinger; Anton Glieder (Database J. Biol. Databases Curation, 2012)