Chemical modification of essential arginine residues associated with the red beet (Beta vulgaris L.) plasma membrane Ca²⁺-ATPase

Two α-dicarbonyl reagents, phenylglyoxal and 2,3-butanedione, were used to demonstrate the presence of essential arginine residues in the mechanism of the plasma membrane Ca²⁺-ATPase of red beet (Beta vulgaris L.) storage tissue. Both the ATP-dependent ⁴⁵Ca²⁺ transport and ITP hydrolytic activities of the Ca²⁺-ATPase were inhibited by these reagents. Optimal inhibition was observed at pH 7.5 and 25°. Inhibition of ATP dependent ⁴⁵Ca²⁺ transport by phenylglyoxal and 2,3-butanedione was decreased by inclusion of ATP in the incubation medium. These results demonstrate that arginine residues are involved in the mechanism of the red beet plasma membrane Ca²⁺-ATPase and may reside at the ATP binding region of the enzyme active site.