The rubiscolins are a group of opioid peptides that are formed during digestion of the ribulose bisphosphate carboxylase/oxygenase (Rubisco) protein from spinach leaves.[1] These peptides have much in common with the better-known gluten exorphins.
There are 2 known rubiscolins with known structure:
Studies have been conducted on rubiscolin structure and biological responses following its digestion.[3][4] The tertiary structure and biological function of spinach-derived rubiscolin has been analyzed in the laboratory.[3] When rubiscolin is digested, studies have shown that rubiscolin has the potential to bind to δ opioid receptors in the body.[3] The analysis of the amino acids responsible for this agonistic relationship of rubiscolin with δ opioid receptors can lead to replication of these proteins in the lab.[3] Rubiscolin has the capability to bind to δ opioid receptors following its digestion.[3] Upon the digestion of rubiscolin from spinach with the protease pepsin, peptides MRWRD, MRW, LRIPVA, AND IAYKPAG were found and purified.[4] These peptides were found to have binding capabilities with angiotensin I-converting enzyme (ACE), which catalyze an antihypertensive, or decreased blood pressure, response.[4] When treated to rats in the laboratory, MRW, MRWRD, and IAYKPAG resulted in antihypertensive responses in hypertensive rats 2 hours, 4 hours, and 4 hours, respectively, after ingestion of the peptides.[4] The peptide LRIPVA did not induce any antihypertensive responses from laboratory rats.[4] The tertiary structure of rubiscolin has been mapped and the δ opioid receptor and ACE binding capabilities have been researched in the lab.[3][4]