Effects of some heavy-metal ions on purified mammalian beta-glucuronidase.

Heavy-metal ions and organic mercurials are known to have a pronounced inhibitory action on many enzymes (see Dixon & Webb, 1958). It is generally accepted that these reagents are reactive towards sulphydryl groups (see Gurd & Wilcox, 1956; Cecil & McPhee, 1959; Boyer, 1959) and also towards other groups (Sohler, Seibert, Kreke & Cook, 1952; Myrback, 1957). A detailed investigation of the effects of heavy-metal ions on a well characterized purified enzyme could lead to a better understanding of both their mode of action and the nature of the active centres in the enzyme. ,-Glucuronidase from various sources is inhibited by fairly low concentrations (less than mm) of mercuric, silver and cupric ions (Sarkar & Sumner, 1950; Jarrige & Henry, 1952; Doyle, Katzman & Doisy, 1955; Levvy, Hay & Marsh, 1957), whilst being unaffected by anionic enzyme poisons such as fluoride, cyanide or iodoacetate (Sarkar & Sumner, 1950; Wong & Rossiter, 1951). The general properties of the enzyme have recently been reviewed by Levvy & Marsh (1959, 1960), who have also studied the effects of heavy-metal ions on ratand mouse-liver f-glucuronidase (Levvy & Marsh, 1957a, b). The present paper is based on similar experiments with a highly purified mam-