Rubiscolin

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.{{Cite book|title=Proteomic applications in biology| vauthors = Heazlewood J |publisher=InTech Manhattan|year=2012|isbn=978-953-307-613-3|location=New York}} 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.{{cite book | vauthors = Cooper GM |title=The Cell: A Molecular Approach |publisher=ASM Press |location=Washington, D.C. |year=2000 |isbn=978-0-87893-106-4 |edition=2nd |chapter=10.The Chloroplast Genome |chapter-url=https://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=RuBisCO&rid=cooper.section.1655#1659 |quote=, 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. |url-access=registration |url=https://archive.org/details/cell00geof }}

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

Studies have been conducted on rubiscolin structure and biological responses following its digestion.{{Cite journal|last1=Caballero|first1=Julio|last2=Saavedra|first2=Mario|last3=Fernández|first3=Michael|last4=González-Nilo|first4=Fernando D.|date=2007-10-01|title=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=Journal of Agricultural and Food Chemistry|volume=55|issue=20|pages=8101–8104|doi=10.1021/jf071031h|pmid=17803260|issn=0021-8561}}{{Cite journal|last1=Yang|first1=Yanjun|last2=Marczak|first2=Ewa D.|last3=Yokoo|first3=Megumi|last4=Usui|first4=Hachiro|last5=Yoshikawa|first5=Masaaki|date=2003-08-01|title=Isolation and Antihypertensive Effect of angiotensin I-Converting Enzyme (ACE) Inhibitory Peptides from Spinach Rubisco|journal=Journal of Agricultural and Food Chemistry|volume=51|issue=17|pages=4897–4902|doi=10.1021/jf026186y|pmid=12903942|issn=0021-8561}} The tertiary structure and biological function of spinach-derived rubiscolin has been analyzed in the laboratory.

When rubiscolin is digested, studies have shown that rubiscolin has the potential to bind to δ opioid receptors in the body. 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. Rubiscolin has the capability to bind to δ opioid receptors following its digestion. 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.{{cite journal |last1=Cassell |first1=Robert J. |last2=Mores |first2=Kendall L. |last3=Zerfas |first3=Breanna L. |last4=Mahmoud |first4=Amr H. |last5=Lill |first5=Markus A. |last6=Trader |first6=Darci J. |last7=van Rijn |first7=Richard M. |title=Rubiscolins are naturally occurring G protein-biased delta opioid receptor peptides |journal=European Neuropsychopharmacology |date=March 2019 |volume=29 |issue=3 |pages=450–456 |doi=10.1016/j.euroneuro.2018.12.013}}

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

• For a key to the single-letter sequences, see {{section link|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.

• Sequence: YPLDL
• From: ?

• Sequence: YPLDLF
• From: ?
• Delta opioid peptide. Can have an anxiolytic effect via activation of sigma1 and dopamine D1 receptors.{{cite journal|title=Rubiscolin-6, a delta opioid peptide derived from spinach Rubisco, has anxiolytic effect via activating sigma1 and dopamine D1 receptors|journal=Peptides|volume=28|issue=10|pages=1998–2003|pmid=17766012|year=2007|last1=Hirata|first1=H|last2=Sonoda|first2=S|last3=Agui|first3=S|last4=Yoshida|first4=M|last5=Ohinata|first5=K|last6=Yoshikawa|first6=M|doi=10.1016/j.peptides.2007.07.024|s2cid=54430089}}

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

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

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

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

{{reflist}}

• {{MeshName|rubiscolin-5}}
• {{MeshName|rubiscolin-6}}

{{Opioidergics}}

Category:Opioid peptides

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