Abstract: The present invention provides an extremely thermostable enzyme obtainable from Thermococcus litoralis. The enzyme, in inorganic pyrophosphatase (sometimes referred to herein as "PPase"), catalyzes the hydrolysis of inorganic pyrophosphate (PPi) to form two molecules of orthophophate (Pi).P.sub.2 O.sub.7.sup.-4 +H.sub.2 O.fwdarw.2HPO.sub.4.sup.-2The present invention also provides a purification process for obtaining the inorganic pyrophosphatase from Thermococcus litoralis. In addition, characterization of the enzyme reveals a multimeric enzyme (125 kDa) with six identical subunits of 20-21 kDa as revealed by SDS-PAGE. Moreover, the enzyme exhibits unusual stability and maintains 100% of its activity after being incubated at 100.degree. C. in the absence of Mg.sup.2+ for 4 hours. Furthermore, the complete amino acid and nucleic acid sequence has been obtained; the amino acid sequence shows similarity to known PPase sequences and likely functional residues appear to be conserved.