Abstract
Our previous studies showed that when ethylmercurithiosalicylate (thimerosal) interacts with the transport ATPase of the guinea pig kidney under specified conditions, the Na + + K +-dependent ATPase activity is inhibited, while the Na +-dependent ATPase, the Na + + ATP-dependent phosphorylation of the enzyme, and the K +-dependent discharge of the phosphoenzyme seem to be unaffected. Here we describe other properties of the thimerosal-treated enzyme: Na +-dependent ADP-ATP exchange, Na +-dependent UTPase, and K +-dependent p-nitrophenylphosphatase activities of the modified enzyme are not inhibited. Kinetics of the Na + effect on the UTPase activities of the native and the modified enzyme are the same. However, K + has a greater inhibitory effect on the Na +-UTPase of the modified enzyme than on the Na +-UTPase of the native enzyme. The increase in the apparent affinity of the thimerosal-treated enzyme for K + is also evident from the kinetics of the K + effect on p-nitrophenylphosphatase. Neither the native enzyme nor the modified enzyme catalyzes a P 1-ATP exchange. The uninhibited activities of the thimerosal-treated enzyme are sensitive to ouabain. These data provide further support for those reaction mechanisms in which the existence of two ATP sites within the enzyme is assumed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.