Methionine sulfoximine (MSO, also known as MetSox) is an irreversible glutamine synthetase inhibitor. It is the sulfoximine derivative of methionine with convulsant effects.
Methionine sulfoximine is composed of two different diastereomers, which are L-S-Methionine sulfoximine and L-R-Methionine sulfoximine. These affect the longevity of the model mouse for Lou Gehrig's disease. Overproduction of glutamate results to excitotoxicity, which kills the cell. Since methionine sulfoximine inhibits glutamate production in the brain, it prevents excitotoxicity. Thus, increasing the longevity of the mice.