This study reports a synergistic photoenzymatic catalysis method for the synthesis of α-tertiary amino acids using threonine aldolases (LTAs) and pyridoxal (PLP)-dependent enzymes. The method involves the α-alkylation of unprotected alanine and glycine with pyridinium salts, facilitated by a Rose Bengal photoredox catalyst. This approach efficiently prepares various α-tertiary amino acids in a single chemical step as a single enantiomer. UV–vis spectroscopy reveals a ternary interaction between the pyridinium salt, protein, and photocatalyst, which is hypothesized to localize radical formation to the active site. The method highlights the potential for combining photoredox catalysts with enzymes to uncover new catalytic functions for known enzymes, offering a promising route for the synthesis of α-tertiary amino acids with enhanced metabolic stability and conformational rigidity.This study reports a synergistic photoenzymatic catalysis method for the synthesis of α-tertiary amino acids using threonine aldolases (LTAs) and pyridoxal (PLP)-dependent enzymes. The method involves the α-alkylation of unprotected alanine and glycine with pyridinium salts, facilitated by a Rose Bengal photoredox catalyst. This approach efficiently prepares various α-tertiary amino acids in a single chemical step as a single enantiomer. UV–vis spectroscopy reveals a ternary interaction between the pyridinium salt, protein, and photocatalyst, which is hypothesized to localize radical formation to the active site. The method highlights the potential for combining photoredox catalysts with enzymes to uncover new catalytic functions for known enzymes, offering a promising route for the synthesis of α-tertiary amino acids with enhanced metabolic stability and conformational rigidity.