Why can't Threonine and Lysine be transaminated?

Answer 1

Hi! Great question. Threonine and lysine both have metabolizing pathways that don't need transamination. It isn't necessarily that they can't be transaminated, our bodies just don't need to transaminate them, because they break them down a different way. Proline isn't transaminated either- but that's becase it's a cyclic amine.