Nov 20, 1975

Calcium-stimulated adenosine triphosphatase in the microsomal fraction of tooth germ from porcine fetus

Biochimica Et Biophysica Acta
F Yoshimura, T Suzuki

Abstract

The characterization and localization of a Ca(2+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) in the tooth germ of the porcine fetus are reported. This enzyme, a microsome fraction, is preferentially activated by Ca(2+). In the presence of 0.5 mM ATP, maximal enzyme activity is obtained at 0.5--1.0 mM CaCl2. The maximal rate of ATP hydrolysis is approx. 20 mumol per h per mg of protein as the enzyme preparation is used here. At optimal Ca(2+) concentration, the Mg(2+) has an inhibitory effect. The enzyme does not require Na+ or/and K+ for activation by Ca(2+). Other nucleotide triphosphates may serve as the substrate, but V for ATP is the highest. The Km for ATP is 8.85 - 10(-5) M. The optimal pH for Ca(2+) activation of the enzyme lies around 9.2. Well known inhibitors of (Na+ + K+)-ATPase, mitochondria ATPase and Ca(2+)-ATPase in the erthrocyte do not inhibit the enzyme. In the subcellular order the enzyme may be assumed to be localized in the smooth endoplasmic reticulum fraction containing cell and Golgi body membrane fragments and in the tissue order in the enamel organ containing an ameloblast layer, stratum intermedium and stellate reticulum.

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References

Mentioned in this Paper

Establishment and Maintenance of Localization
Cations, Divalent
Calcium [EPC]
Ca(2+)-Transporting ATPase
Fetal Structures
Entire Fetus
Stratum Intermedium
Golgi Apparatus
Calcium
Adenosine Triphosphatases

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