Non-ribosomal incorporation of arginine into a specific protein by a cell-free extract of parathyroid tissue

Both cell-free extracts and postribosomal supernatants of bovine parathyroid glands incorporated [¹⁴C] arginine from a mixture of ¹⁴C-labeled amino acids into protein and specifically into a protein with electrophoretic properties similar to those of parathyroid hormone. A single-step Edman degradation removed 75% of the [¹⁴C] arginine from radioactive proteins. These observations indicate that parathyroid tissue contains a soluble enzyme that catalyzes the incorporation of arginine into the amino terminus of parathyroid proteins including either parathyroid hormone or a closely related protein.