Purification and characterization of lysosomal H(+)-ATPase. An anion-sensitive v-type H(+)-ATPase from rat liver lysosomes.

Lysosomal H(+)-ATPase was purified to homogeneity from rat liver lysosomes. It is a bafilomycin A1-sensitive Mg(2+)-ATPase, which reacts with antibodies against the 16- and 70-kDa subunits of vacuolar H(+)-ATPase (Nezu, J., Motojima, K., Tamura, H., and Ohkuma, S. (1992) J. Biochem. (Tokyo) 112, 212-219), and has been separated from both the N-ethylmaleimide (NEM)-sensitive/bafilomycin A1-insensitive Mg(2+)-ATPase (ATPase I) and the NEM-insensitive Mg2+/Ca(2+)-ATPase (ATPase II) (Hayashi, H., Arai, K., Sato, O., Shimaya, A., Sai, Y., and Ohkuma, S. (1992) Chem. Pharm. Bull. 40, 2783-2786). The purified enzyme had the subunit structure of vacuolar H(+)-ATPase, consisting of 110-, 70-, 56-, 42-, 39-, 34-, (32-,) and 16-kDa proteins. It had optimal activity at a pH of 7.0-8.0, with an apparently single Km value for ATP of 95 microM. It hydrolyzed ATP > or = dATP >> GTP, ITP >> UTP, but not CTP, and was inhibited by ADP. It demonstrated divalent cation specificity in the order of Mg2+, Mn2+ > Fe2+, Co2+ > Ca2+. Among various anions, Cl-, Br-, and F- activated ATPase activity, whereas NO3- inhibited activity. It was inhibited not only by bafilomycin A1 but also by NEM, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, quercetin, and dicyclohexylcarbodi-imide. The purified enzyme was incorporated into proteoliposomes where its proton pump activity was reconstituted. This suggested that the isolated enzyme maintains its H+ translocation activity. These findings suggest that the isolated enzyme is an anion-sensitive vacuolar type H(+)-ATPase that functions as a lysosomal proton pump.