= M. Kunitz
{c}
<M. Kunitz> isolated crystalline <inorganic pyrophosphatase> from yeast and characterized its catalytic activity in a 1952 study. The purified <protein> accelerated <hydrolysis> of <pyrophosphate> to separate <phosphate> units. By testing a purified preparation, the experiment could connect a reaction to a particular <enzyme> rather than merely observing that an unfractionated biological extract changed its <reaction substrate>.<Crystalline inorganic pyrophosphatase isolated from baker's yeast by M. Kunitz>[abstract, isolation and catalytic specificity]{ref}
A revealing result was the requirement for activating <metal> <ions>, including <magnesium>. The <reaction rate> also depended on <pH>, temperature and the amounts of <enzyme> and <reaction substrate>. Related organic phosphate compounds were not equivalent substrates for this preparation. Thus a shared chemical linkage does not guarantee recognition by the same <enzyme>. As a simple assay illustration, complete cleavage of 10 micromolar <pyrophosphate> produces 20 micromolar additional <phosphate> units. Measuring that increase requires subtracting any <phosphate> already present; measuring an initial <reaction rate> further requires a time interval before substantial substrate depletion.<Crystalline inorganic pyrophosphatase isolated from baker's yeast by M. Kunitz>[abstract, activating ions, rate dependence and tested organic compounds]{ref}
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