ADENOSINETRIPHOSPHATASE OF MYTILUS SPERMATOZOA. I. EFFECTS OF pH, CALCIUM AND MAGNESIUM, AND CONCENTRATION OF ENZYME AND SUBSTRATE

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Abstract
1. The tails of the sperm of Mytilus edulis dephosphorylate ATP. 2. MgCl2 (5 x 10-4 M) increases the rate of the enzyme activity in 0.02 M KCl to more than double that of the control; the same concentration of CaCl2 causes about 25% greater activity than the control. 3. In appropriate concentrations magnesium potentiates the effect of calcium, but all concentrations of calcium tested depress the magnesium activation. 4. The enzyme activity rises gradually to a fairly sharp peak at pH 8.4 in veronal and glycine buffers and drops off abruptly to pH 10. 5. The rate of dephosphorylation of ATP is proportional to the enzyme concentration. 6. Phosphorylysis is also a function of the ATP concentration, except at higher levels of ATP. 7. This is apparently a true ATP-ase since only about 50% of the labile phosphate is liberated with appreciable velocity from ATP.

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