Final answer:
The bovine preproinsulin is first converted to proinsulin by the removal of specific amino acids, forming the inactive storage form. Active insulin results from the cleavage of the proinsulin's 'C' chain, thereby producing the functional hormone composed of A and B chains. The primary structure of these chains is critical for the hormone's function.
Step-by-step explanation:
The sequence of insulin bovine preproprotein consists of a series of steps that eventually leads to the production of active insulin. Initially, insulin is synthesized as preproinsulin, which then undergoes conversion to proinsulin after the N-terminal end (comprising 23 amino acids) is removed. Proinsulin contains an additional 'C' chain of 35 amino acids, making it the inactive storage form of insulin. Active insulin is formed when this 'C' chain is cleaved by proteolytic enzymes, separating the A and B chains of insulin, which in bovine insulin consist of 21 and 30 amino acids respectively. The primary structure of these chains is indicated by three-letter abbreviations for the amino acids.
The manufacturing of synthetic human insulin, or humulin, involves a similar precursor sequence where the A and B chains are initially isolated and then reconnected through disulfide cross bridges. This is achieved by synthesizing the required DNA sequences for the A and B polypeptide chains and then expressing them in E. coli using recombinant DNA technology. These steps underscore the importance of the unique primary structure of the insulin polypeptides, as even slight variations can alter its function.