Other · Plant protein-derived opioid pentapeptide
Rubiscolin-5
Also known as —
Spinach Rubisco-derived pentapeptide used to investigate δ-opioid receptor recognition and the role of peptide length.
- Length
- 5 amino acids
- Half-life
- Not well characterised
- Mechanism
- Rubiscolin-5 is a δ-opioid receptor (DOR; OPRD1)-preferring agonist identified through opioid-sensitive functional assays. DOR activation engages Gi/o-associated signalling, although potency and efficacy require characterisation in each receptor-expression system.
- Studied in
- Isolated tissue assays, recombinant opioid receptor systems and peptide structure–activity studies examine its δ-opioid pharmacology and relationship to Rubiscolin-6.
About Rubiscolin-5
Rubiscolin-5 has the sequence Tyr–Pro–Leu–Asp–Leu and a free C-terminal carboxyl group. It was described in 2001 during investigation of opioid-active peptides generated by pepsin digestion of spinach ribulose-1,5-bisphosphate carboxylase/oxygenase, commonly called Rubisco. The sequence lies within the enzyme's large subunit. It belongs to the exorphin group: peptides released from external protein sources that display opioid receptor activity in experimental assays under defined conditions.
The principal receptor association is with the δ-opioid receptor, rather than the μ-opioid preference of endomorphins. Early characterisation used isolated tissue responses and pharmacological antagonism to assess opioid activity. Rubiscolin-5 is particularly useful alongside Rubiscolin-6 because the pair differs by one C-terminal phenylalanine. This comparison helps investigate how terminal extension changes receptor recognition, functional activity and susceptibility to proteolysis without altering the shared five-residue core.
Laboratory notes
- Verify the native free-acid terminus; C-terminal amidation creates a different analogue.
- Resolve Rubiscolin-5 from Rubiscolin-6 and other Rubisco fragments chromatographically when working with protein hydrolysates.
- Use selective DOR blockade and parallel MOR/KOR controls where receptor selectivity is an experimental endpoint.
Storage and reconstitution basics: storage guide.
Questions about Rubiscolin-5
What protein supplies the Rubiscolin-5 sequence?
The sequence occurs in the large subunit of spinach Rubisco, the enzyme involved in photosynthetic carbon fixation.
How does it differ from Rubiscolin-6?
Rubiscolin-5 is Tyr–Pro–Leu–Asp–Leu. Rubiscolin-6 adds a phenylalanine at the C-terminus.
Does its origin establish that free Rubiscolin-5 is abundant in intact leaves?
No. Identification in a protein digest establishes a releasable sequence, not the abundance of the free peptide in intact plant tissue.
Is Rubiscolin-5 for human use?
No. It is supplied strictly for in-vitro laboratory research and is not for human or animal consumption.
Related research peptides
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