Rubiscolin

Class of opioid peptides From Wikipedia, the free encyclopedia

The rubiscolins are a group of opioid peptides that are formed during digestion of the ribulose bisphosphate carboxylase/oxygenase (Rubisco) protein from spinach leaves. Two of them are known,^[1] acting as weak agonists of the delta opioid receptor selective for the G protein signaling pathway.^[2]

Background

Rubisco is a key protein in carbon fixation and is found in photosynthetic organs such as leaves in very high concentration. It usually accounts for 40% of the protein mass of a plant.^[3] With all forms of RuBisCO (not only plants, but also bacteria) taken into account, RuBisCO is possibly the most abundant type of protein on Earth.^[4]

The production of similar peptides from digestion of other species' Rubisco has not yet been reported.

Overview

Studies have been conducted on rubiscolin structure and biological responses following its digestion.^[5]^[6] The tertiary structure and biological function of spinach-derived rubiscolin has been analyzed in the laboratory.^[5]

When rubiscolin is digested, studies have shown that rubiscolin has the potential to bind to δ opioid receptors in the body.^[5] 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.^[5] Rubiscolin has the capability to bind to δ opioid receptors following its digestion.^[5] Rubiscolin-5 and -6 are unusual delta opioid receptor agnoists in that they mainly activate the G protein signaling pathway at the receptor, mostly leaving the β-arresting pathway alone.^[2]

Types of rubiscolin

Several peptides are known to be produced after digestion of rubiscolin in various ways.

For a key to the single-letter sequences, see Amino acid § Table of standard amino acid abbreviations and properties.
All peptides sequences are assumed to start with NH₂- and end with -COOH, unless otherwise stated.

Rubiscolin-5

Sequence: YPLDL
From: ?

Rubiscolin-6

Sequence: YPLDLF
From: ?
Delta opioid peptide. Can have an anxiolytic effect via activation of sigma1 and dopamine D1 receptors.^[7]

Other bioactive Rubisco-derived peptides

MRW

Sequence: MRW
From: peptin digestion.
Binds angiotensin-converting enzyme (ACE). Reduces the blood pressure of hypertensive rats, 2 hours after ingestion.^[6]

MRWRD

Sequence: MRWRD
From: peptin digestion.
Binds angiotensin-converting enzyme (ACE). Reduces the blood pressure of hypertensive rats, 4 hours after ingestion.^[6]

IAYKPAG

Sequence: IAYKPAG
From: peptin digestion.
Binds angiotensin-converting enzyme (ACE). Reduces the blood pressure of hypertensive rats, 4 hours after ingestion.^[6]

LRIPVA

Sequence: LRIPVA
From: peptin digestion.
Binds angiotensin-converting enzyme (ACE). No effects on blood pressure of hypertensive rats.^[6]

References

[1]
Yang, Shuzhang; Yunden, Jinsmaa; Sonoda, Soushi; Doyama, Naomi; Lipkowski, Andrzej W; Kawamura, Yukio; Yoshikawa, Masaaki (2001). "Rubiscolin, a δ selective opioid peptide derived from plant Rubisco". FEBS Letters. 509 (2): 213–217. doi:10.1016/S0014-5793(01)03042-3. PMID 11741591. S2CID 83631217.
[2]
Cassell, Robert J.; Mores, Kendall L.; Zerfas, Breanna L.; Mahmoud, Amr H.; Lill, Markus A.; Trader, Darci J.; van Rijn, Richard M. (March 2019). "Rubiscolins are naturally occurring G protein-biased delta opioid receptor peptides". European Neuropsychopharmacology. 29 (3): 450–456. doi:10.1016/j.euroneuro.2018.12.013.
[3]
Heazlewood J (2012). Proteomic applications in biology. New York: InTech Manhattan. ISBN 978-953-307-613-3.
[4]
Cooper GM (2000). "10.The Chloroplast Genome". The Cell: A Molecular Approach (2nd ed.). Washington, D.C.: ASM Press. ISBN 978-0-87893-106-4. , one of the subunits of ribulose bisphosphate carboxylase (rubisco) is encoded by chloroplast DNA. Rubisco is the critical enzyme that catalyzes the addition of CO₂ to ribulose-1,5-bisphosphate during the Calvin cycle. It is also thought to be the single most abundant protein on Earth, so it is noteworthy that one of its subunits is encoded by the chloroplast genome.
[5]
Caballero, Julio; Saavedra, Mario; Fernández, Michael; González-Nilo, Fernando D. (2007-10-01). "Quantitative Structure–Activity Relationship of Rubiscolin Analogues as δ Opioid Peptides Using Comparative Molecular Field Analysis (CoMFA) and Comparative Molecular Similarity Indices Analysis (CoMSIA)". Journal of Agricultural and Food Chemistry. 55 (20): 8101–8104. doi:10.1021/jf071031h. ISSN 0021-8561. PMID 17803260.
[6]
Yang, Yanjun; Marczak, Ewa D.; Yokoo, Megumi; Usui, Hachiro; Yoshikawa, Masaaki (2003-08-01). "Isolation and Antihypertensive Effect of angiotensin I-Converting Enzyme (ACE) Inhibitory Peptides from Spinach Rubisco". Journal of Agricultural and Food Chemistry. 51 (17): 4897–4902. doi:10.1021/jf026186y. ISSN 0021-8561. PMID 12903942.
[7]
Hirata, H; Sonoda, S; Agui, S; Yoshida, M; Ohinata, K; Yoshikawa, M (2007). "Rubiscolin-6, a delta opioid peptide derived from spinach Rubisco, has anxiolytic effect via activating sigma1 and dopamine D1 receptors". Peptides. 28 (10): 1998–2003. doi:10.1016/j.peptides.2007.07.024. PMID 17766012. S2CID 54430089.