S-adenosyl-L-methionine-dependent transferase that acts as a component of the wyosine derivatives biosynthesis pathway. Catalyzes the transfer of the alpha-amino-alpha-carboxypropyl (acp) group from S-adenosyl-L-methionine to 4-demethylwyosine (imG-14), forming 7-aminocarboxypropyl-demethylwyosine (wybutosine-86) at position 37 of tRNA(Phe)