Mg-Dependent, Zn-ATPase: Enzymatic Characteristics, Ion Specificities and Tissue Distribution

Mg-Dependent, Zn-ATPase: Enzymatic Characteristics, Ion Specificities and Tissue Distribution Mucosal crude microsomes, prepared from proximal rat small intestine, exhibited significant Mg-dependent, Zn-ATPase activity; V max = 23 μmoles Pi/mg protein/hr, K m = 160 nm, and Hill Coefficient, n= 1.5. Partial purification (∼10-fold) was achieved by detergent extraction, and centrifugation through 250 mm sucrose: V max = 268 units, K m = 1 nm, and n= 6. In partially purified preparations, the assay was linear with time to 60 min, and with protein concentration to 1 μg/300 μl. Activities at pH 8 and 8.5 were higher than at pH 7.2. The ATP K m was 0.7 mm, with an optimal ATP/Mg ratio of ∼2. Ca elicited ATPase activity but did not augment the Zn-dependent activity. In partially purified preparations, the homologous salts of Co, Cd, Cu, and Mn exhibited no detectable activity. Vanadate inhibition studies yielded two component kinetics with a K i of 12 μm for the first component, and 96 μm for the second component, in partially purified preparations. Tissue distribution analyses revealed gradients of activity. In the proximal half of the small intestine, Mg/Zn activity increased progressively from crypt to villus tip. In long axis studies, this activity decreased progressively from proximal to distal small bowel. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Mg-Dependent, Zn-ATPase: Enzymatic Characteristics, Ion Specificities and Tissue Distribution

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 2001 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s0023200100037
Publisher site
See Article on Publisher Site

Abstract

Mucosal crude microsomes, prepared from proximal rat small intestine, exhibited significant Mg-dependent, Zn-ATPase activity; V max = 23 μmoles Pi/mg protein/hr, K m = 160 nm, and Hill Coefficient, n= 1.5. Partial purification (∼10-fold) was achieved by detergent extraction, and centrifugation through 250 mm sucrose: V max = 268 units, K m = 1 nm, and n= 6. In partially purified preparations, the assay was linear with time to 60 min, and with protein concentration to 1 μg/300 μl. Activities at pH 8 and 8.5 were higher than at pH 7.2. The ATP K m was 0.7 mm, with an optimal ATP/Mg ratio of ∼2. Ca elicited ATPase activity but did not augment the Zn-dependent activity. In partially purified preparations, the homologous salts of Co, Cd, Cu, and Mn exhibited no detectable activity. Vanadate inhibition studies yielded two component kinetics with a K i of 12 μm for the first component, and 96 μm for the second component, in partially purified preparations. Tissue distribution analyses revealed gradients of activity. In the proximal half of the small intestine, Mg/Zn activity increased progressively from crypt to villus tip. In long axis studies, this activity decreased progressively from proximal to distal small bowel.

Journal

The Journal of Membrane BiologySpringer Journals

Published: May 1, 2001

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