Occurrence and characteristics of {sup18}O-exchange reactions catalyzed by sodium- and potassium-dependent adenosine triphosphatases

Technical Report · Sat Jan 01 00:00:00 EST 1972

DOI:https://doi.org/10.2172/4485348· OSTI ID:4485348

Dahms, A S; Boyer, P D

Microsomal preparations of the (NA{sup+},K{sup+})-ATPase from porcine outer medulla and electroplax catalyzed a rapid Mg{sup2+-} and K{sub+-}dependent exchange of water oxygens with inorganic phosphate in the absence of ATP or ADP. Exchange activity was unaffected by uncouplers and inhibitors of oxidative phosphorylation but was inhibited by Na{sup+}, ouabain, N,N{prime}-dicyclohexylcarbodiimide, or p-mercuribenzoate. No nucleotide requirement for the exchange could be demonstrated. Addition of ATP to a NA{sup+}-inhibited system resulted in an exchange of oxygens of medium P{subi} concomitant with ATP hydrolysis. This ATP-induced exchange amounted 1.5 oxygen atoms per P{subi} released. Neither ADP nor adenylyl methylene diphosphonate would serve to activate the exchange. Treatment of the preparations with deoxycholate apparently uncoupled the medium P{subi} {l_reversible} HOH exchange but was without affect on the ATP-induced exchange. The data suggest that the exchange arises by partial reversal of a late step in ATP hydrolysis by the (Na{sup+},K{sup+})-ATPase.

• Research Organization: University of California, Los Angeles (USA)
• Sponsoring Organization: US - Atomic Energy Commission (AEC)
• DOE Contract Number: AT(04-3)-34
• NSA Number: NSA-28-005275
• OSTI ID: 4485348
• Report Number(s): UCLA--34-P-102-36
• Country of Publication: United States
• Language: English

Related Subjects

*OXYGEN 18-- ISOTOPIC EXCHANGE
ATP-ASE
CATALYSIS
CHEMICAL REACTION KINETICS
N40230* --Chemistry--Inorganic
Organic
& Physical Chemistry--Isotope Exchange & Isotope Separation
POTASSIUM COMPOUNDS
SODIUM COMPOUNDS
WATER