Orexin A’s chemical structure is C152H243N47O44S4 - 152 carbon atoms, 243 hydrogen atoms, 47 nitrogen atoms, 44 oxygen atoms, and 4 sulfur atoms.
Orexin B’s chemical structure is C123H212N44O35S - 123 carbon atoms, 212 hydrogen atoms, 44 nitrogen atoms, 35 oxygen atoms, and a singular sulfur atom.
There are two types of orexin - A and B. The difference between them is in the chemical structure: orexin A is 33 amino acid residues long, and has two intrachain SS-bonds, whereas orexin B is only 28 amino acid residues long and is linear. Scientists believe orexin A may be more biologically important than B, but have yet to find convincing proof.
Orexin is only produced by a small cluster of glands in the hypothalamus - the part of the forebrain that lies below the thalamus and co-ordinates our autonomic nervous systems and homeostatic systems (body temperature, hunger, thirst etc.) -, a number ranging from 100 000 - 200 000 neurons releasing this hormone into the brain.
glands and types of orexin