Large-Scale Refolding and Enzyme Reaction of Human Preproinsulin for Production of Human Insulin

Insulin evolution: A holistic view of recombinant production advancements

The increased prevalence of diabetes and the growing popularity of non-invasive methods of recombinant human insulin uptake, such as oral insulin, have increased insulin demand, further limiting the affordability of insulin. Over 40 years have passed since the development of engineered microorganisms that replaced the animal pancreas as the primary source of insulin. To stay ahead of the need for insulin in the present and the future, a few drawbacks with the existing expression systems need to be alleviated, including the inclusion body formation, the use of toxic inducers, and high process costs. To address these bottlenecks and improve insulin production, a variety of techniques are being used in bacteria, yeasts, transgenic plants and animals, mammalian cell lines, and cell-free expression systems. Different approaches for the production of insulin, including two-chain, proinsulin or mini-proinsulin, preproinsulin coupled with fusion protein, chaperone, signal peptide, and purification tags, are explored in upstream, whereas downstream processing takes into account the recovery of intact protein in its bioactive form and purity. This article focuses on the strategies used in the upstream and downstream phases of the bioprocess to produce recombinant human insulin. This review also covers a range of analytical methods and tools employed in investigating the genuity of recombinant human insulin.

Vortex Fluidic Mediated Oxidative Sulfitolysis of Oxytocin

In peptide production, oxidative sulfitolysis can be used to protect the cysteine residues during purification, and the introduction of a negative charge aids solubility. Subsequent controlled reduction aids in ensuring correct disulfide bridging. In vivo, these problems are overcome through interaction with chaperones. Here, a versatile peptide production process has been developed using an angled vortex fluidic device (VFD), which expands the viable pH range of oxidative sulfitolysis from pH 10.5 under batch conditions, to full conversion within 20 min at pH 9–10.5 utilising the VFD. VFD processing gave 10-fold greater conversion than using traditional batch processing, which has potential in many applications of the sulfitolysis reaction.

Downstream processing of recombinant human insulin and its analogues production from E. coli inclusion bodies

The Global Diabetes Compact was launched by the World Health Organization in April 2021 with one of its important goals to increase the accessibility and affordability of life-saving medicine-insulin. The rising prevalence of diabetes worldwide is bound to escalate the demand for recombinant insulin therapeutics, and currently, the majority of recombinant insulin therapeutics are produced from E. coli inclusion bodies. Here, a comprehensive review of downstream processing of recombinant human insulin/analogue production from E. coli inclusion bodies is presented. All the critical aspects of downstream processing, starting from proinsulin recovery from inclusion bodies, inclusion body washing, inclusion body solubilization and oxidative sulfitolysis, cyanogen bromide cleavage, buffer exchange, purification by chromatography, pH precipitation and zinc crystallization methods, proinsulin refolding, enzymatic cleavage, and formulation, are explained in this review. Pertinent examples are summarized and the practical aspects of integrating every procedure into a multimodal purification scheme are critically discussed. In the face of increasing global demand for insulin product, there is a pressing need to develop a more efficient and economical production process. The information presented would be insightful to all the manufacturers and stakeholders for the production of human insulins, insulin analogues or biosimilars, as they strive to make further progresses in therapeutic recombinant insulin development and production.

Truncated Thioredoxin Peptides Serves as an Efficient Fusion Tag for Production of Proinsulin

BACKGROUND

Insulin is a peptide hormone used for regulating blood glucose levels. Human insulin market is projected to grow at a rate of 12.5% annually. To meet the needs of patients, a cost effective insulin manufacturing strategy has to be developed. This can be achieved by selecting a competent host, ideal fusion tag and streamlined downstream process.

OBJECTIVE

In this article, we have demonstrated that selecting a right fusion partner for expression of toxic proteins like insulin, plays a major role in increasing the recombinant protein yield.

METHODS

In this article, we have focused on identifying a peptide tag fusion partner for expressing proinsulin by truncating thioredoxin tag. Truncations were carried out from both Amino and Carboxy terminus of the protein and efficiency of truncated sequences was evaluated by expressing it with proinsulin gene. FCTRX (1-15) sequence fused to proinsulin was processed further to establish downstream protocol for purification.

RESULTS

Thioredoxin tag was truncated appropriately by considering the fusion tag: protein ratio. A couple of sequences ranging 10 - 15 amino acids were identified based on its in silico properties. Of these FCTRX (1-15) showed increased expression and stability of fusion protein. 156 mg of purified insulin was generated from 1g of inclusion body after enzymatic conversion and chromatographic steps.

CONCLUSION

As a result of the current study, it was concluded that FCTRX (1-15) peptide has advantageous attributes to be considered as an ideal fusion tag for expression of proinsulin. This can be further explored by expressing it with other proteins.

Improving the refolding efficiency for proinsulin aspart inclusion body with optimized buffer compositions

Successfully recovering proinsulin's native conformation from inclusion body is the crucial step to guarantee high efficiency for insulin's manufacture. Here, two by-products of disulfide-linked oligomers and disulfide-isomerized monomers were clearly identified during proinsulin aspart's refolding through multiple analytic methods. Arginine and urea are both used to assist in proinsulin refolding, however the efficacy and possible mechanism was found to be different. The oligomers formed with urea were of larger size than with arginine. With the urea concentrations increasing from 2 M to 4 M, the content of oligomers decreased greatly, but simultaneously the refolding yield at the protein concentration of 0.5 mg/mL decreased from 40% to 30% due to the increase of disulfide-isomerized monomers. In contrast, with arginine concentrations increasing up to 1 M, the refolding yield gradually increased to 50% although the content for oligomers also decreased. Moreover, it was demonstrated that not redox pairs but only oxidant was necessary to facilitate the native disulfide bonds formation for the reduced denatured proinsulin. An oxidative agent of selenocystamine could increase the yield up to 80% in the presence of 0.5 M arginine. Further study demonstrated that refolding with 2 M urea instead of 0.5 M arginine could achieve similar yield as protein concentration is slightly reduced to 0.3 mg/mL. In this case, refolded proinsulin was directly purified through one-step of anionic exchange chromatography, with a recovery of 32% and purity up to 95%. All the results could be easily adopted in insulin's industrial manufacture for improving the production efficiency.