Abstract
Abstract The specific activity of a magnesium-dependent, inorganic pyrophosphatase, active at neutral pH, was determined in crude hemolysates prepared from the erythrocytes of 10 normal subjects, 19 patients with arthritis other than pseudogout, and 13 patients with definite pseudogout. The enzyme activity measured 3 different ways gave comparable results; no differences were evident except for a wider range in the pseudogout group. Calcium, ferrous, ferric, and cupric ions failed to substitute for magnesium in the reaction, and all but ferric ions completely inhibited the enzyme when present in concentrations equimolar to that of magnesium. More purified preparations from the pseudogout patients showing the highest and lowest specific activities were compared with that from a normal subject by polyacylamide gel electrophoresis and isoelectric focusing. A single broad band in the former and a single peak in the latter were found. There is no evidence of deficiency of this enzyme in pseudogout patients, although it is possible that inhibition of a similar enzyme in synovial tissues by metal ions may contribute to the calcium pyrophosphate deposits that have been found in patients with hyperparathyroidism and hemochromatosis.
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