Abstract
Rat liver mitochondria essentially free of endogenous Ca 2+ show low initial rate of energy-dependent Ca 2+ uptake. Preincubation of mitochondria under de-energized conditions in the presence of small amounts of external Ca 2+ results in a 8–10-fold time-dependent increase of energy-dependent Ca 2+ uptake. Ca 2+-dependent activation of the Ca 2+-transporting system follows first-order kinetics ( t 1 2 ∼ 1 min in the presence of 5 μM Ca 2+ at 20°C). Ca 2+-activated mitochondria demonstrate a simple hyperbolic initial rate-Ca 2+ concentration dependence, whereas strong apparent cooperativity is observed in the velocity-substrate curves for Ca 2+-depleted mitochondria. It is concluded that apparent cooperativity of the energy-dependent Ca 2+ uptake is due to slow (as compared with the ‘turnover number’) activation of a Ca 2+-specific uniporter which is inactive in the absence of external Ca 2+.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
