Liver glucose-6-phosphatase activity is not modulated by physiological intracellular Ca2+ concentrations.
1. In the presence of MgATP and increasing amounts of added Ca2+, isolated liver microsomal vesicles accumulate approx. 10 nmol of Ca2+/mg of protein and buffer ambient free Ca2+ at increasing concentrations (0.22-10.9 microM). Under these experimental conditions, microsomal glucose-6-phosphatase activity is unaffected by the concentration of extravesicular free Ca2+. 2. Different levels of intravesicular Ca2+ were obtained by treating microsomes with the Ca2+ ionophore A23187 and by stimulating active microsomal Ca2+ accumulation with Pi (3 mM). In both instances, microsomal glucose-6-phosphatase activity is unaffected by the level of intravesicular Ca2+.
Fulceri
R
R
Istituto di Patologia Generale, University of Siena, Italy.
Bellomo
G
G
Gamberucci
A
A
Benedetti
A
A
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D005952:Glucose-6-Phosphatase / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains
D000001:Calcimycin; D000255:Adenosine Triphosphate; D005952:Glucose-6-Phosphatase; D002118:Calcium