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

Two alpha-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 Ca-45(2+) transport and ITP hydrolytic activities of the Ca2+-ATPase were inhibited by these reagents. Optimal inhibition was observed at pH 7.5 and 25 degrees. Inhibition of ATP dependent Ca-45(2+) 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.