Which of the following is true w.r.t. manufacture of genetically engineered insulin ?

Options

A. C-peptide must be removed during maturation of insulin. This was the main challenge for the production of insulin using rDNA techniques
B. Eli Lily company was the first one to produce Humulin on commercial scale
C. Chain A and chain B of insulin are held together by disulphide linkages
D. All of these

Answer

To determine which statements are true regarding the manufacture of genetically engineered insulin, we can analyze the information provided in the video transcript step by step.

### Step-by-Step Solution:

1. **Understanding Insulin Structure**:
- Insulin is initially synthesized as a pro-hormone that includes three polypeptide chains: Chain A, Chain B, and Chain C.
- In the mature form of insulin, Chain C is removed, leaving only Chains A and B.

**Hint**: Remember the structure of insulin and the role of the C-peptide.

2. **Role of C-Peptide**:
- The C-peptide must be removed during the maturation of insulin. This is a crucial step in the production of insulin using recombinant DNA technology.

**Hint**: Focus on the maturation process of insulin and the significance of the C-peptide.

3. **Historical Context**:
- The Eli Lilly company was the first to produce human insulin (Humulin) on a commercial scale. This marked a significant advancement in diabetes treatment.

**Hint**: Recall the historical milestones in the production of insulin.

4. **Chemical Bonds in Insulin**:
- Chains A and B of insulin are linked together by disulfide linkages (or disulfide bridges), which are essential for the stability of the insulin molecule.

**Hint**: Understand the importance of disulfide bonds in protein structure.

5. **Conclusion**:
- All the statements provided in the options are true:
- C-peptide must be removed during maturation of insulin.
- This was a challenge in recombinant DNA techniques.
- Eli Lilly was the first to produce Humulin commercially.
- Chains A and B are held together by disulfide linkages.

**Final Answer**: Therefore, the correct option is "all of these."