Methionine sulfoximine (MSO) is an irreversible glutamine synthetase inhibitor. It is the sulfoximine derivative of methionine with convulsant effects.
D-methionine sulfoxide hydrochloride, the D-isomer of methionine sulfoxide hydrochloride, is the oxidation product of methionine. Methionine is a restrictive amino acid in milk or legume proteins and is easily oxidized during storage.