Enzymatic semisynthesis of insulin specifically labelled with tritium at position B-30

We have synthesized porcine insulin labelled with tritium at position B-30 using enzyme-catalysed formation of a peptide bond. The resulting insulin derivative has the label in the expected position and is biologically active. We have tested our procedure to prepare batches up to 50 muCi of tritiated insulin at a specific radioactivity of up to 1.14 Ci/mmol.