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). 4-demethylwyosine(37) in tRNA(Phe) + S-adenosyl-L-methionine = 4-demethyl-7-[(3S)-3-amino-3-carboxypropyl]wyosine(37) in tRNA(Phe) + H(+) + S-methyl-5'-thioadenosine Belongs to the class I-like SAM-binding methyltransferase superfamily. TRM5/TYW2 family.