Disease relevance of PPA2

• When the bovine PPase cDNA was expressed in Escherichia coli, catalytically active PPase was produced that comigrated with bovine retinal PPase in a nondenaturing gel and was clearly distinguishable from the host PPase [1].

High impact information on PPA2

• These results demonstrate that hydrolysis of cytosolic PPi is essential for yeast growth and that this function is not substantially affected by the intrinsic characteristics of the PPase protein that accomplishes it [2].
• Our structures of the yeast PPase product complex at 1.15 A and fluoride-inhibited complex at 1.9 A visualize the active site in three different states: substrate-bound, immediate product bound, and relaxed product bound [3].
• Yeast exopolyphosphatase (scPPX) processively splits off the terminal phosphate group from linear polyphosphates longer than pyrophosphate. scPPX belongs to the DHH phosphoesterase superfamily and is evolutionarily close to the well characterized family II pyrophosphatase (PPase) [4].
• The effects of fluoride on the Y-PPase variants confirmed that PPase catalysis involves two enzyme.PP(i) intermediates, which bind fluoride with greatly different rates (Baykov, A. A., Fabrichniy, I. P., Pohjanjoki, P., Zyryanov, A. B., and Lahti, R. (2000) Biochemistry 39, 11939-11947) [5].
• Mutations at P2 subsite residues (Y93F and K56R) caused a much greater decrease in phosphate binding affinity of yeast PPase in the presence of Mn(2+) or Co(2+) than mutations at P1 subsite residues (R78K and K193R) [6].

Biological context of PPA2

• The new gene, PPA2, is located on chromosome 13 and encodes a protein whose sequence is 49% identical to the cytoplasmic enzyme [7].
• Uncouplers stimulate the PPase activity several-fold in mitochondria from both cells that overexpress PPA2 from a high copy number plasmid and cells with normal expression [8].
• We conclude that the mitochondrial PPase encoded by PPA2 is essential for mitochondrial function and maintenance of the mitochondrial genome [7].
• The deduced amino acid sequence is 49.5% identical to that of PPase from Saccharomyces cerevisiae, and contains identical amino acid residues at all of the positions previously identified as essential for catalytic activity in that enzyme [1].
• This sequence information was used to clone PPase cDNA from a retinal cDNA library [1].

Anatomical context of PPA2

• The other, PPA2, is located in the mitochondria and appears to be energy-linked [9].
• This stimulation is much higher, whereas basal PPase activity is lower, in isotonic than in hypotonic solution, which indicates that intact membranes are a prerequisite for maximal effects [8].
• Phosphoprotein phosphatases (PPase) were isolated from either the rabbit cerebral cortex or Baker's yeast by excluding endogenous megamodulin with histone, and then by desalting cations with Bio-Gel P-6DG filtration [10].

Associations of PPA2 with chemical compounds

• This activity was further stimulated 3-fold by the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone, which suggests that PPA2 is part of an energy-linked enzyme [7].
• All amino acids known to be important for catalysis are conserved, except one glutamate which is substituted by an aspartate in PPA2 [9].
• Extracts of soluble proteins from bovine retina contain multiple species of inorganic pyrophosphatase (PPase) that can be resolved by hydroxylapatite or ion exchange chromatography [1].
• Soluble inorganic pyrophosphatase (PPase), which converts inorganic pyrophosphate (PP(i)) into usable phosphate, is almost universally present as a central enzyme of phosphorus metabolism and uses divalent metal ion as a necessary cofactor [11].
• Soluble inorganic pyrophosphatase (PPase) is one of the better understood phosphoryl-transfer enzymes and is distinctive in having four divalent metal ions at the active site [12].

Other interactions of PPA2

• Yeast PPA2 gene encodes a mitochondrial inorganic pyrophosphatase that is essential for mitochondrial function [7].

References