Evidence for a metalloprotein stucture of plasma membrane 5' ‐nucleotidase

Abstract

To point out the metalloprotein structure of bovine liver plasma membrane 5 ' -nucleotidase, we studied the inhibition mechanism of the purified enzyme by EDTA: this apparently non-competitive inhibition seems to be dependent on EDTA concentration, pH, temperature and incubation time. When the restoration of activity was assayed by addition of divalent cations or by gel filtration, the inhibition became progressively irreversible with time. Incubation of the enzyme with [14C]EDTA allowed us to observe, after gel filtration as well as after sucrose gradient ultracentrifugation, that the chelating agent is bound to 5 ' -nucleotidase. '-NucleotidaseMetalloprotein

Purification, characterization and cellular localization of 5′-nucleotidase from Torpedo electric organ

“…5'-Nucleotidase appears to be a metalloenzyme, and metal-ion chelators such as EDTA and EGTA inhibit enzyme activity. The nature of the endogenous cation is still uncertain (Harb et al, 1984). The enzyme purified from Torpedo electric organ, like that in other tissues, is activated by the addition of Mg2+, whereas Zn2+ is a very strong inhibitor (Tanaka et al, 1973;Stefanovich et al, 1976;Cammer et al, 1980;Mallol & Bozal, 1983;Meflah et al, 1984b).…”