Activation of sea-urchin sperm motility is accompanied by an increase in the creatine kinase exchange flux.
The kinetics of the creatine kinase (CK) reaction were studied in suspensions of quiescent and active, intact sea-urchin spermatozoa in artificial seawater, using 31P-NMR magnetization transfer. In inactive sperm, no CK-mediated exchange flux was detected, whereas in activated motile sperm, the forward pseudo-first-order rate constant was 0.13+/-0.04 s-1 at 10 degrees C, corresponding to a steady-state CK flux of 3.1+/-0.5 mM.s-1. Intracellular pH shifted from 6.6+/-0.1 to 7.6+/-0.1 upon activation. The phosphocreatine (PCr)/ATP and PCr/Pi ratios were only marginally reduced in activated sperm, whereas the estimated cytosolic free ADP concentration increased remarkably from 9 microM in quiescent, to 114 microM in activated spermatozoa. The elevation of CK flux upon sperm activation is discussed in the light of the proposition that in sea-urchin spermatozoa, which are fuelled entirely by oxidative phosphorylation, high-energy phosphate transport is mediated by a 'CK/PCr shuttle'.
Dorsten
F A
FA
Department of in vivo NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Bolognalaan 50, NL-3584 CJ Utrecht, The Netherlands.
Wyss
M
M
Wallimann
T
T
Nicolay
K
K
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003401:Creatine / Q000378:metabolism; D003402:Creatine Kinase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D010085:Oxidative Phosphorylation; D010710:Phosphates / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D012617:Sea Urchins; D013081:Sperm Motility; D013094:Spermatozoa / Q000201:enzymology*; D013696:Temperature
D010710:Phosphates; D010725:Phosphocreatine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003402:Creatine Kinase; D003401:Creatine