TY - JOUR
T1 - Ca2+-dependent ATPases in the basolateral membrane of rat kidney cortex
AU - Tsukamoto, Y.
AU - Suki, Wadi N.
AU - Liang, C. T.
AU - Sacktor, B.
PY - 1986
Y1 - 1986
N2 - The basolateral segment of the rat renal tubular plasma membrane possesses Ca2+-dependent ATPase activity which was independent of Mg2+. Two kinetic forms were found: one, was a high affinity (apparent K(m) for free Ca2+ of 172 nM) low capacity (V(max) of 144 nmol of P(i)·min-1·mg-1 protein) type; the other, had low affinity (apparent K(m) of 25 μM) and high capacity (896 nmol of P(i)·min-1·mg-1 protein). Mg2+ inhibited both Ca2+-ATPases. The high affinity enzyme exhibited positive cooperativity with respect to ATP, with a n value of 1.6. Ca2+-ATPase activity was not affected by calmodulin and was not inhibited by vanadate. On the other hand, both high and low affinity Ca2+-ATPase activities were increased when 1,25-dihydroxycholecalciferol was given to vitamin D-deficient rats. Kinetically, the enhanced activities were due to an increase in the V(max) values; the apparent affinities for free Ca2+ were not changed. The physiological function of the vitamin D-sensitive, Mg+-independent, Ca2+-ATPase activities remains to be established.
AB - The basolateral segment of the rat renal tubular plasma membrane possesses Ca2+-dependent ATPase activity which was independent of Mg2+. Two kinetic forms were found: one, was a high affinity (apparent K(m) for free Ca2+ of 172 nM) low capacity (V(max) of 144 nmol of P(i)·min-1·mg-1 protein) type; the other, had low affinity (apparent K(m) of 25 μM) and high capacity (896 nmol of P(i)·min-1·mg-1 protein). Mg2+ inhibited both Ca2+-ATPases. The high affinity enzyme exhibited positive cooperativity with respect to ATP, with a n value of 1.6. Ca2+-ATPase activity was not affected by calmodulin and was not inhibited by vanadate. On the other hand, both high and low affinity Ca2+-ATPase activities were increased when 1,25-dihydroxycholecalciferol was given to vitamin D-deficient rats. Kinetically, the enhanced activities were due to an increase in the V(max) values; the apparent affinities for free Ca2+ were not changed. The physiological function of the vitamin D-sensitive, Mg+-independent, Ca2+-ATPase activities remains to be established.
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M3 - Article
C2 - 2419321
AN - SCOPUS:0022931546
SN - 0021-9258
VL - 261
SP - 2718
EP - 2724
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 6
ER -