Α-Endorphin

α-Endorphin (alpha-endorphin) is an endogenous opioid peptide with a length of 16 amino acids, and the amino acid sequence: Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-Lys-Ser-Gln-Thr-Pro-Leu-Val-Thr. With the use of mass spectrometry, Nicholas Ling was able to determine the primary sequence of a-endorphin.

Relation to beta- and gamma-endorphin
Endorphins are generally known as neurotransmitters that are released when the body goes into pain. The three endorphins that play a role in this response are α-endorphin, β-endorphin (beta-endorphin), and γ-endorphin (gamma-endorphin) which are all derived from the same polypeptide known as pro-opiomelanocortin. Although all play roles as neurotransmitters, the specific effects of all three differ. The most studied endorphin of the three is β-endorphin. α-Endorphins are known to contain one less amino acid than γ-endorphins, differing by a single leucine amino acid at the terminal end. Although this may seem minor, It allows them to have vastly different effects. Studies found that γ-endorphins and α-endorphins have opposite effects which allow them to help maintain a level of homeostasis within the brain and behavior of animals. All of the specific effects on the body of α-endorphins are not yet fully studied nor fully understood by the science community. However, some studies suggest that these endorphins behave similarly to amphetamines. Similarly, other studies agree that Alpha-endorphins effects are similar to psychostimulant drugs.

Ranking based length, α-endorphins are the shortest with 16 amino acid residues. Meanwhile, the β-endorphin has the longest chain which begins with the same 16 amino acids as α-Endorphins: Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-Lys-Ser-Gln-Thr-Pro-Leu-Val-Thr. The same sequence is also present in γ-endorphin. The beginning Tyr-Gly-Gly-Phe-Met chain is also known as the N-terminal pentapeptide opioid sequence. With such configuration, endorphins act as agonists to opioid receptors in the brain.

Effects on behavior
Studies have shown that α-endorphin is the strongest peptide in delaying avoidance behaviors. α-Endorphin has the same C-terminal sequence of β-LPH, allowing these peptides to have a high affinity for opiate binding sites. Even a slight difference in the C-terminal amino acid can have drastic effects on avoidance behavior. The importance in sequencing determines the function of the endorphin. When an N-terminal amino acid such as tyrosine is removed, there seems to be no significant impacts on avoidance behavior. However, when there are adjustments to the C-terminal sequence, like removing β-LPH 61-65; activity of the endorphin decreases.