Structure and mechanism of a cysteine sulfinate desulfinase engineered on the aspartate aminotransferase scaffold

► We engineer aspartate aminotransferase to change substrate and reaction specificity. ► Substitutions (I33Q/Y214Q/R280Y) generate a cysteine sulfinate desulfinase. ► Desulfinase to transaminase activity fold enhancement in the mutant enzyme is 105. ► X-ray structures of engineered enzyme in PLP, PMP and alanyl-PLP forms solved. ► Mutated residues are present in naturally occurring desulfinases and decarboxylases.