title: Mg-dependent, Zn-ATPase: enzymatic characteristics, ion specificities and tissue distribution.
abstract: Mucosal crude microsomes, prepared from proximal rat small intestine, exhibited significant Mg-dependent, Zn-ATPase activity; Vmax = 23 micromoles Pi/mg protein/hr, Km = 160 nm, and Hill Coefficient, n = 1.5. Partial purification (approximately 10-fold) was achieved by detergent extraction, and centrifugation through 250 mm sucrose: Vmax = 268 units, Km = 1 nm, and n = 6. In partially purified preparations, the assay was linear with time to 60 min, and with protein concentration to 1 microg/300 microl. Activities at pH 8 and 8.5 were higher than at pH 7.2. The ATP Km was 0.7 mm, with an optimal ATP/Mg ratio of approximately 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 Ki of 12 microm for the first component, and 96 microm 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.
authors.affiliation: Columbia Genome Center of the College of Physicians & Surgeons of Columbia University, New York, NY 10032, USA.
authors.forename: A
authors.initials: A
authors.lastname: Wang
authors.forename: N
authors.initials: N
authors.lastname: Cortas
authors.forename: I S
authors.initials: IS
authors.lastname: Edelman
mesh_terms: D000251:Adenosine Triphosphatases / Q000302:isolation & purification* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004386:Duodenum / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000201:enzymology*; D007583:Jejunum / Q000201:enzymology*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008970:Molecular Weight; D009928:Organ Specificity; D051381:Rats; D017207:Rats, Sprague-Dawley; D013379:Substrate Specificity; D014638:Vanadates / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D014638:Vanadates; D000251:Adenosine Triphosphatases; C434316:Mg-dependent, Zn-ATPase; D008274:Magnesium; D015032:Zinc; D002118:Calcium