Chemoenzymatic Synthesis of ³⁶S Isotopologues of Methionine and <i>S</i>‑Adenosyl‑l‑methionine

Substrates containing isotope labels at specific atoms are required for transition-state analysis based on the measurement of multiple kinetic isotope effects.³⁶S-labeled l-methionine and <i>S</i>-adenosyl-l-methionine were synthesized from elemental sulfur using a chemoenzymatic approach with >98% ³⁶S enrichment. This method provides access to previously inaccessible sulfur isotope-labeled substrates for sulfur kinetic isotope effect studies