Isovaline is a rare
amino acid transported to Earth by the
Murchison meteorite[citation needed], which landed in
Australia in 1969. The discovery of isovaline in the
biosphere demonstrates an extraterrestrial origin of amino acids and has been linked to the
homochirality of life on Earth,[1] suggesting a role in the origin of life.[2]
Isovaline is an
isomer of the common amino acid
valine, with the position of one methyl group shifted slightly (from position 3 to position 2). The structure of isovaline is also somewhat similar to the amino acids
GABA and
glycine, the chief inhibitory
neurotransmitters in the
mammaliancentral nervous system. Isovaline acts as an analgesic in mice[3][4] by activating peripheral
GABAB receptors.[4][5] In a mouse model of
osteoarthritis isovaline restored mobility, suggesting inhibition of nociception by isovaline in the synovial membrane of the mouse knee.[4]
Isovaline does not cross the
blood–brain barrier[4] and does not enter into the brain or spinal cord. Drugs such as
opioids cross the blood–brain barrier to produce analgesia but often produce in addition confusion, sedation, and
addiction.
Isovaline acts downstream to the
cyclooxygenase system that
NSAIDs inhibit, suggesting a means to avoid adverse effects such as irritation of the
gastrointestinal system.
^J.R. Cronin; S. Pizzarello (1999). "Amino acid enantiomer excesses in meteorites". Origin and Significanca Adv. Space Rex. 23 (2): 293–299.
doi:
10.1016/s0273-1177(99)00050-2.
^Mindy Levine; Craig Scott Kenesky; Daniel Mazori; Ronald Breslow (2008). "Enantioselective Synthesis and Enantiomeric Amplification of Amino Acids under Prebiotic Conditions". Organic Letters. 10 (12): 2433–2436.
doi:
10.1021/ol8007099.
PMID18491865.