Studies on phosphoribosylpyrophosphate synthetase from Giardia intestinalis

A substantial degree of purification, up to 3200-fold, with recoveries of 8-11% of phosphoribosylpyrophosphate (P-Rib-PP) synthetase from Giardia intestinalis extracts was achieved by the high resolution techniques of anion exchange chromatography and chromatofocusing columns on a fast protein liquid chromatography system. A Mono P chromatofocusing column gave rise to an enzyme peak eluting from the column at pH 4.5, indicating that the enzyme has an isoelectric point (pI) at approximately this value. The molecular weight of the enzyme was found to be 150,000 from a Sephacryl S-200 column. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the purified enzyme gave a single protein band with a subunit molecular weight of 38,000, indicating that the enzyme existed as a tetramer. The properties of G. intestinalis P-Rib-PP synthetase in terms of pH optimum, isoelectric point, subunit structure, phosphate requirement, metal and nucleotide specificity, appear to be very similar to those of the enzyme from other sources.