title: The kinetics and divalent cation inhibition of plasma membrane ATPase in the yeast Candida albicans.
abstract: The kinetics of ATP hydrolysis and cation effects on ATPase activity in plasma membrane from Candida albicans ATCC 10261 yeast cells were investigated. The ATPase showed classical Michaelis-Menten kinetics for the hydrolysis of Mg X ATP, with Km = 4.8 mM Mg X ATP. Na+ and K+ stimulated the ATPase slightly (9% at 20 mM). Divalent cations in combination with ATP gave lower ATPase activity than Mg X ATP (Mg greater than Mn greater than Co greater than Zn greater than Ni greater than Ca). Divalent cations inhibited the Mg X ATPase (Zn greater than Ni greater than Co greater than Ca greater than Mn). Free Mg2+ inhibited Mg X ATPase weakly (20% inhibition at 10 mM). Computed analyses of substrate concentrations showed that free Zn2+ inhibited Zn X ATPase, mixed (Zn2+ + Mg2+) X ATPase, and Mg X ATPase activities. Zn X ATP showed high affinity for ATPase (Km = 1.0 mM Zn X ATP) but lower turnover (52%) relative to Mg X ATP. Inhibition of Mg X ATPase by (free) Zn2+ was noncompetitive, Ki = 90 microM Zn2+. The existence of a divalent cation inhibitory site on the plasma membrane Mg X ATPase is proposed.
authors.forename: M J
authors.initials: MJ
authors.lastname: Hubbard
authors.forename: P A
authors.initials: PA
authors.lastname: Sullivan
authors.forename: M G
authors.initials: MG
authors.lastname: Shepherd
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D002176:Candida albicans / Q000201:enzymology*; D002462:Cell Membrane / Q000201:enzymology; D007700:Kinetics; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
chemical_list: D000255:Adenosine Triphosphate; D012964:Sodium; D000251:Adenosine Triphosphatases; D015032:Zinc; D011188:Potassium