riboflavin synthase activity https://github.com/geneontology/go-ontology/issues/30193 6,7-dimethyl-8-(1-D-ribityl)lumazine:6,7-dimethyl-8-(1-D-ribityl)lumazine 2,3-butanediyltransferase activity riboflavine synthase activity vitamin B2 synthase activity Catalysis of the reaction: 2 6,7-dimethyl-8-(1-D-ribityl)lumazine + H+ = 5-amino-6-(D-ribitylamino)uracil + riboflavin. EC:2.5.1.9 RHEA:20772 heavy riboflavin synthase riboflavin synthetase activity riboflavine synthetase activity KEGG_REACTION:R00066 MetaCyc:RIBOFLAVIN-SYN-RXN GO:0004746 molecular_function light riboflavin synthase transferase activity, transferring alkyl or aryl (other than methyl) groups