The influence of chemical and physical factors on the Ca++ ATPase and Na+-K+ activated ATPase ac-
tivities in human red blood, cell membrane were investigated and the following results were obtained.
1. Substrate specifies for RBCiMF and the original supernatent fraction were examined. The nucleoside triphosphatase activity of RBCMF has the specificity only for ATP. However, RBC\CIE ´ supernatant has a high nucleoside triphosphatase activity with all nucleotides used. On the other hand, the original supernatant splits all nucleoside triphosphates in the presence of NIg´+ only without Carr in the incubation, medium.
2. Influence of incubation temperature shoved that the optimum temperature of incubation was 40´C and 50´C for Ca++ ATPase and Na+-K+ATPase, respectively. In this system, Ca++ATPase was almost completely inhibited at 50´C which was the optimum temperature for Na+-K+ATPase activity.
3. The Ca++ATPase activity was maximum at a Ca´ concentration of 5X 10-4M and fell off as the Ca´ concentration was either increased or decreased.
4. Both -\a+-K+ATPase and Ca++ATPase had the highest activity when they were preincubated in the medium of pH 6. 0, and their activities decreased in a parallel manner as the pH of the preincubating medium deviated from pH6.0.
5. Activities of both Na+-K+ATPase and Ca++ATPase decreased in the parallel fashion after sonification of the enzymes with intensities greater than 60w.
6. The longer the duration of pretreatment of enzymes with trypsin, the stronger were the inhibition of both Na`-K+ATPase and Ca`-ATPase. However, Ca+´´ATPase was much more suscentible to the trypsin treatment than Na+-K´ ATPase.
7. Pretreatment of RBCVIF with phospholipase D had no effect on either Na- -K+ATPase or Ca´ I ATPase whereas the pretreatment: with phospholipase A and C inhibited only Ca++ ATPase. The Cal- ATPase activity after phospholipase A and C treatment was inhibited by 35% and 3410 of the control level, respectively.
8. Phospholipase A treatment interfers with the dephosphorylation mechanism of Ca++ATPase, whereas phospholipase C interfere with the phcsphorylation mechanism of Ca?+ATPase activity.
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