Two routes to the same molecule
Solid-phase peptide synthesis (SPPS) builds a peptide one amino acid at a time on a resin bead, using protected building blocks and repeated chemical steps. Recombinant expression inserts the gene into a host such as a bacterium or yeast and lets the cell make the peptide, which is then purified.
Length and complexity
SPPS is efficient for short peptides. Each coupling step is slightly less than perfect, so yield and purity fall as the chain gets longer. Recombinant expression is not limited by chain length in the same way, which is why longer peptides and small proteins, insulin being the classic example, are made this way.
Modifications
SPPS gives the chemist full control. Non-natural amino acids, D-amino acids, cyclisation and terminal modifications are straightforward to build in. Recombinant systems make natural L-amino-acid sequences; further changes are usually added afterwards by chemistry, or by engineering the host.
Scale and cost
Chemical synthesis consumes large volumes of solvents and expensive protected amino acids, and these costs scale directly with batch size. Recombinant processes need upfront investment in strain, expression and fermentation development, but at large volume the cost per gram can fall considerably, especially for longer molecules.
Impurity profiles
- Chemical synthesis: deletion and truncation products, racemised residues and residual solvents or reagents.
- Recombinant: host-cell proteins, residual DNA, endotoxin and product-related variants.
Neither profile is better in the abstract. What matters is that the impurities are identified, controlled by the purification process, and measured by methods that can detect them.
A simple decision guide
- Short peptide, heavily modified or with non-natural residues: chemical synthesis is usually the practical route.
- Long peptide or small protein with a natural sequence, needed at large scale: recombinant expression is often more economical.
- Natural sequence plus one chemical modification: a hybrid route can combine the two.
Theertha Biopharma works on recombinant peptides, including a high-expression platform, PepXen™, for insulins, GLP-1s and recombinant peptides. See recombinant peptides or talk to our team.
Frequently asked questions
What is the difference between recombinant and synthetic peptides?
Synthetic peptides are built chemically one amino acid at a time. Recombinant peptides are made by living cells carrying the gene for the peptide and then purified.
Which route is cheaper?
It depends on length and scale. Chemical synthesis suits short peptides and small batches; recombinant production often becomes more economical for longer molecules at large volume.
Can recombinant systems make modified peptides?
They make natural amino-acid sequences. Further modification is usually added by chemistry after expression, or by engineering the host.
General information for readers in biopharmaceutical development; not regulatory or medical advice.