Expressing Of Salmon Calcitonin In E. Coli And Its Pharmacological Activity Study

Calcitonin is one of the most important peptides in metabolism of calcium and phosphorous and in development and differentiation of bone.We aimed to express recombinant salmon calcitonin (rsCT) in Escherichia coli., however sCT and many polypeptides need carboxy amidation for full activity or prolonged bioavailability, this modification is not possible in prokaryotes.A method of using self-cleaving Intein expression system was used in this study, the system is able to making amidated sCT and some other peptides by using special buffers with ammonia during the self-cleaving of the C-terminal Intein. In this study, we cloned sCT gene into pTWIN 1 vector and used E. coli strain ER2566 as the host. Expression experiments were carried out both in shake flasks and a 5L bioreactor. Purified rsCT was identified with RT-HPLC and isoelectric focusing. Biological assays of rsCT were based on osteoclastic cells responsiveness and blood calcium determination in rats.The results show that most of the rsCT is in form of amidation after self-cleaving by Inteins and has good effect of hypocalcemic bioactivity.