Alkaline inorganic pyrophosphatase from guar (Cyamopsis tetragonoloba) cotyledons

Popli, Sarla; Singh, Randhir

doi:10.1016/s0031-9422(00)86685-6

Cited by 8 publications

(1 citation statement)

References 13 publications

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“…Soluble alkaline pyrophosphatases have been characterized in plant extracts and some of them have been purified (Naganna et al, 1954;Gould and Winget, 1973;Klemme and Jacobi, 1974;Popli and Singh, 1977;Kumar and Singh, 1983;Mukherjee and Pal, 1983;Ho and Khoo, 1985;Ananda Krishnan and Gnanam, 1988;Gama Branda0 and Aoyama, 1992;MortainBertrand et al, 1992). Based on the subcellular fractionation studies carried out by Gross and ap Rees (1986) and by Weiner et al (1987), it is likely that most of these soluble alkaline activities correspond to plastidic isoforms.…”

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Molecular Cloning and Characterization of a Soluble Inorganic Pyrophosphatase in Potato

et al. 1995

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A cDNA clone encoding a soluble inorganic pyrophosphatase (EC 3.6.1 .l) of potato (Solanum tuberosum 1.) was isolated by screening a developing tuber library with a heterologous probe. The central domain of the encoded polypeptide is nearly identical at the sequence leve1 with its Arabidopsis homolog (J.J. Kieber and E.R.Signer [1991] Plant MOI Biol 16: [345][346][347][348]. Computer-assisted analysis of the potato, Arabidopsis, and Escherichia coli soluble pyrophosphatases indicated a remarkably conserved organization of the hydrophobic protein domains. The enzymatic function of the potato protein could be deduced from the presence of amino acid residues highly conserved in soluble pyrophosphatases and was confirmed by its capacity to complement a thermosensitive pyrophosphatase mutation i n E. coli. The potato polypeptide was purified from complemented bacterial cells and its pyrophosphatase activity was shown to be strictly dependent on Mg2+ and strongly inhibited by Ca2+. The subcellular location of the potato pyrophosphatase is unknown. Structure analysis of the N-terminal protein domain failed to recognize typical transit peptides and the calculated molecular m a s of the polypeptide (24 kD) is significantly inferior to the values reported for the plastidic (alkaline) or mitochondrial pyrophosphatases in plants (28-42 kD). Two unlinked loci could be mapped by restriction fragment length polymorphism analysis in the potato genome using the full-length cDNA as probe.Inorganic pyrophosphatases (EC 3.6.1.1) are ubiquitous enzymes catalyzing the hydrolysis of PPi into two Pi's. PPi hydrolysis is highly exergonic (AG" = -33.5 kJ mol-l) and provides a thermodynamic driving force to a range of anabolic processes. Most notably, the synthesis of biological polymers produces PPi either during the activation of monomers (e.g. ADP-Glc synthesis prior to starch elongation, amino acid activation into amino acyl-tRNA prior to polypeptide elongation) or during the elongation of the polymers (eg. DNA and RNA synthesis, polyisoprene [rubber] synthesis). According to the Kornberg (1962) model, the energy "wasted" by PPi hydrolysis is needed for making these processes thermodynamically irreversible. Hence, the first and most ubiquitous function of inorganic pyrophosphatases is presumably to drive anabolism.

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