ADENOSINETRIPHOSPHATASE OF MYTILUS SPERMATOZOA. II. EFFECTS OF SULFHYDRYL REAGENTS, TEMPERATURE AND INORGANIC PYROPHOSPHATE

¹ Department of Anatomy, University of Chicago, Chicago 37, Ill. and Marine Biological Laboratory, Woods Hole, Mass.

1. Mytilus sperm tail ATP-ase temperature coefficient (Q₁₀) = 2; temperature optimum occurs in the range between 20° and 30° C.

2. The sperm tails actively dephosphorylate sodium pyrophosphate (NaPP) as well as ATP. Two separate enzymes are involved, which together with their substrates apparently compete for the magnesium ions in the medium.

3. K_M-ATP-ase= 3.1 x 10^-4; K_M-IPP-ase = 4.3 x 10^-5.

4. In low concentrations of ATP and NaPP, the amount of inorganic phosphate liberated is additive, while at higher concentrations, inhibition occurs.

5. ATP-ase is more sensitive than IPP-ase to sulfhydryl inhibition, although iodoacetate has only slight effect on both enzymes.

6. An hypothesis is proposed that regulation of the undulatory flagellar wave primarily resides within the flagellum itself, and is a function of the reciprocal activity of two enzymes, ATP-ase in the contraction phase, and IPP-ase in the relaxation phase.