Catalysis of the reaction: 5-amino-6-(D-ribitylamino)uracil + L-tyrosine + S-adenosyl-L-methionine = 2-iminoacetate + 5'-deoxyadenosine + 5-amino-5-(4-hydroxybenzyl)-6-(D-ribitylimino)-5,6-dihydrouracil + H+ + L-methionine.
5-amino-6-(D-ribitylamino)uracil--L-tyrosine 4-hydroxyphenyl transferase activity