Phenylglyoxal suppresses cationic lysine/K+ symport under alkaline conditions in brush border membrane vesicles from larval Manduca sexta midgut.

The arginine-specific reagent, phenylglyoxal, decreases the initial rate of lysine/K+ symport (cotransport) as well as maximum lysine accumulation at pH 9.2, by brush border membrane vesicles obtained from the larval midgut of the lepidopteran, Manduca sexta. The symport of a neutral amino acid, leucine, remained unaffected. Following exposure to phenylglyoxal, the apparent dissociation constant for lysine increased by a factor of 2.5 whereas the maximum uptake rate decreased by a factor of 0.4. More than one arginine residue appears to react with phenylglyoxal. Apparently phenylglyoxal reacts preferentially with arginine residues on a symporter that is specific for positively charged lysine. Phenylglyoxal shows promise as a specific covalent label for the identification of a cationic amino acid symporter.