A microsomal fraction was isolated from rabbit psoas muscle by a modification of Muscatello's method. The fraction contained a Mg-dependent ATPase which had a pH optimum of 7.5. Activity was further stimulated by addition of Na or K or other monovalent cations to the reaction mixture, but synergistic activation by Na and K, and ouabain inhibition, could not be demonstrated. The enzyme hydrolyzed only ATP (adenosine triphosphate) and ITP (inosine triphosphate) at appreciable rates, but Na or K stimulated activity only when ATP was used as substrate. Activity was inhibited by Ca and by low concentrations of Na deoxycholate, and was sensitive to inhibition by thiol group reagents. The enzyme could be distinguished from another enzyme, also present in the fraction, which was Ca-activated, and which exhibited a wider substrate specificity, different pH activation characteristics, lower specific activity, lack of stimulation by Na or K, and less sensitivity to inhibition by deoxycholate and by thiol group reagents. These findings formed the basis for demonstration of the Mg-dependent ATPase in situ.
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1 December 1966
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December 01 1966
CYTOCHEMISTRY OF PHOSPHATASES OF THE SARCOPLASMIC RETICULUM : I. Biochemical Studies
A. G. Engel,
A. G. Engel
From the Division of Neuropathology and Department of Pathology, College of Physicians and Surgeons, Columbia University, New York.
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Lois W. Tice
Lois W. Tice
From the Division of Neuropathology and Department of Pathology, College of Physicians and Surgeons, Columbia University, New York.
Search for other works by this author on:
A. G. Engel
From the Division of Neuropathology and Department of Pathology, College of Physicians and Surgeons, Columbia University, New York.
Lois W. Tice
From the Division of Neuropathology and Department of Pathology, College of Physicians and Surgeons, Columbia University, New York.
Dr. Engel's present address is the Section of Neurology, Mayo Clinic, Rochester, Minnesota. Dr. Tice's present address is the Laboratory of Physical Biology, National Institute of Arthritis and Metabolic Diseases, Bethesda, Maryland
Received:
December 15 1965
Online ISSN: 1540-8140
Print ISSN: 0021-9525
Copyright © 1966 by The Rockefeller University Press
1966
J Cell Biol (1966) 31 (3): 473–487.
Article history
Received:
December 15 1965
Citation
A. G. Engel, Lois W. Tice; CYTOCHEMISTRY OF PHOSPHATASES OF THE SARCOPLASMIC RETICULUM : I. Biochemical Studies . J Cell Biol 1 December 1966; 31 (3): 473–487. doi: https://doi.org/10.1083/jcb.31.3.473
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