Aminomutation catalyzed by CO ₂ self-sufficient cascade amino acid decarboxylases

Molecular editing of an amino group from α-position of amino acids to its β-position is of scientific interest and could be economically appealing. Here we reconstructed an in vitro biotransformation pathway composed of two cascade decarboxylases, i.e., aspartate β-decarboxylase and aspartate α-decarboxylase, and implemented molecular editing to change α-alanine into β-alanine. In it, we discovered a new reaction of aspartate β-decarboxylase that can fix CO ₂ directly. This cascade enzymatic pathway enabled an aminomutation reaction with 100% carbon atom economy. This work presented the first CO ₂ -fixing biological reaction catalyzed by the amino acid decarboxylases and demonstrated a new means for the molecular editing of α-amino acids.