Arylsulphatase activity in milk and rennet from different sources

Arylsulphatase activity on two substrates, p-nitrocatechol sulphate (pNCS) and p-nitrophenyl sulphate (pNPS), in milk and commercial rennet from different sources was measured. Cows' and sheep's milk contained arylsulphatase active on pNCS, and batch pasteurization reduced the activity. Rennets from animal sources, including calf, kid and lamb, exhibited arylsulphatase activity with different substrate specificities. A fermentation-produced chymosin from a genetically engineered microorganism did not exhibit detectable arylsulphatase activity. A commercial rennet paste showed arylsulphatase activity after dialysis.