Modification of an essential arginine residue associated with the plasma membrane ATPase of red beet ( Beta vulgaris L.) storage tissue

The dicarbonyl compounds, phenylgloxyl and 2,3-butanedione were used to demonstrate the presence of an essential arginine residue in the mechanism of the red beet ( Beta vulgaris L.) plasma membrane ATPase. Treatment of the red beet ATPase with either of these reagents resulted in an inhibition of ATP hydrolytic activity protectable by the inclusion of either ATP or ADP during inhibitor incubation. Ligands of the ATP hydrolytic reaction also protected against phenylglyoxyl inhibition and affected the ability of ADP to protect against inhibition by this reagent. Kinetic analysis of 2,3-butanedione and phenylglyoxyl inhibition suggested the presence of a single arginine residue susceptible to attack by these reagents. As similar results with these arginine modification reagents were found for both the plasma membrane-associated and solubilized forms of the ATPase, it is apparent that the function of this arginyl moiety is not affected by detergent treatment and removal of the enzyme from the membrane.