<p>Endopolyphosphatases are enzymes that hydrolyse long inorganic phosphate chains to shorter chains of (predominantly) 60 or 3 phosphate units. The <taxon tax_id="4932">Saccharomyces cerevisiae</taxon> (Baker's yeast) member, Ppn1p, is an essential vacuolar enzyme [<cite idref="PUB00016147"/>]. It is a homodimer of chains of about 350 amino acids derived by proteolysis, from the amino end, of the precursor sequence. This region contains the metallophosphoesterase domain, which is found in a large number of proteins with phosphoesterase activity.</p>