A Novel Bovine Spinal Cord Endoprotease with High Specificity for Dynorphin B

An endopeptidase that converts the opioid peptide dynorphin B (Tyr-Gly-Gly-Phe-Leu-Arg-aRg-Gln-Phe-Lys-Val-Val-Thr) to its bioactive fragment Leu-enkephalin-Arg6 was isolated from bovine spinal cord. The enzyme was purified about 230-fold from a concentrated spinal cord extract. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, it stained as a protein of Mr 55,000. The purified enzyme is optimally active at around pH7 and has essential thiol groups. It appears to be highly specific for dynorphin B (Km = 11 microM) but not for alpha-neoendorphin or dynorphin A, two other opioids included in the prodynorphin precursor. From its specificity, molecular size, and inhibitory spectrum, this enzyme is different from other known dynorphin-converting or -degrading enzymes and appears to be a unique and novel endoprotease.