methyltransferase activity 3',4',5'-trimethylmyricetin 3-O-methyltransferase activity https://github.com/geneontology/go-ontology/issues/28199 Catalysis of the reaction: 3',4',5'-O-trimethylmyricetin + S-adenosyl-L-methionine = 3,3',4',5'-O-tetramethylmyricetin + S-adenosyl-L-homocysteine. molecular_function MetaCyc:RXN-13918 GO:0102440 RHEA:74771