Subcellular localization of inorganic pyrophosphatases in rabbit skeletal muscle and some properties of a microsomal acid pyrophosphatase.

Abstract

Subcellular localization of muscle inorganic pyrophosphatase was examined using rabbit skeletal muscle homogenates. The pyrophosphatases were found to be contained in the microsomal, mitochondrial, and cytosol fractions. The microsomal and mitochondrial pyrophosphatases were most likely bound to the respective subcellular fractions. The pyrophosphatases associated with microsome and mitochondria showed their optimal activities at about pH 5.5 and 7, respectively. They were not dissociated from the particles by washing with salt solution or by ten times freezing-thawing. The activity of microsomal acid pyrophosphatase was not affected by Mg,2+ Ca,2+ or EDTA, but that of the mitochondrial neutral pyrophosphatase was enhanced by the addition of Mg.2+ The microsomal acid pyrophosphatase was stable between pH values of 5.5 and 8.5 during storage at 4°. The activity was inhibited by p-chloromercuribenzoate. The activity was irreversibly inhibited by sodium dodecyl sulfate, but reversibly inhibited by neutral sa...