D-ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the pivotal enzyme for carbon dioxide fixation and photorespiration in plants, and it is known that rubisco makes up approximately 30 to 50 % of the soluble protein found in the leaves of plants. Rubisco is the most abundant protein on earth. Rubiscolin-6 is an opioid peptide derived from the large subunit of rubisco during digestion in animals. Spinach is a green leafy vegetable that, like all leaves, contains rubisco and therefore can be a good source of rubiscolin-6. Evidence suggests that rubiscolin-6 may have particular mood elevating properties on account of its ability to interact with dopamine and opioid receptors in animals (and possible humans). For example, in one study, researchers reported anxiolytic effects for rubiscolin-6, and that these anxiolytic effects were blocked by opioid receptors. The anxiolytic effects were also blocked by dopamine D1 antagonists but not dopamine D2 antagonists. These results therefore suggest that rubiscolin-6 may interact with dopamine D1 and opioid receptors to cause elevations in mood.
Eat Well, Stay Healthy. Protect Yourself