Purification and properties of bovine liver lysosomal adenosine 5'-phosphosulphate sulphohydrolase. A non-specific enzyme with pyrophosphatase and phosphodiesterase activities

Observations on the biological roles of sulphatases

Until recently little was known about the biological roles played by sulphatase enzymes, owing in part to the selection of assay substrates that were convenient but only removely related to the natural substrates. Once this was recognized the elucidation of function proceeded more rapidly. Microbial sulphatases appear to have roles to play in the nutrition of individual microorganisms whilst collectively they enable sulphur, returned to soils and waters in the form of sulphate esters, to be made available for recycling. In contrast, with one or two important exceptions, mammalian sulphatases are concerned, in association with other enzymes, with the turnover of macromolecules. Still defying understanding are the roles of sulphatases acting on adenosine 5'-phosphosulphate (APT) and 3'-phosphoadenosine 5'-phosphosulphate (PAPA). APS sulphatases have now been purified from ox-liver lysosomes and cytosol and from a strain of Comamonas terrigena. The lysosomal enzyme shows wide specificity and can hydrolyse ATP, ADP, FED and pyrophosphate. The cytosol enzyme is apparently specific and may be active only when cellular concentrations of ATP are low. The bacterial enzyme is also specific and has properties and a cellular localization that suggest the possibility of its involvement in sulphate transport.

Studies on pyrophosphate diesterase activity in cultured human fibroblasts: a deficiency in Niemann-Pick disease

Fibroblast phosphodiesterase activity was studied using 4-methylumbelliferyl pyrophosphate diester as substrate. Release of the fluorogen, 4-methylumbelliferone, was found to be dependent on acid phosphatase activity, normally present in excess in crude cell extracts. Phosphodiesterase activity had an acid pH optimum, was deficient in Niemann-Pick disease fibroblasts, and, when assayed in the presence of exogenous acid phosphatase, had an identical electrofocusing profile to that of sphingomyelinase. These findings suggest that 4-methylumbelliferyl pyrophosphate diesterase and acid sphingomyelinase activities are dependent on the same enzyme.