Key result
Classical steady state enzyme kinetics are difficult to apply to actomyosin ATPase because the conditions required for actin activation cause myosin aggregation and actomyosin precipitation.
This basic science study investigates the steady-state kinetics of actin-activated heavy meromyosin and subfragment-1 ATPases to better understand the molecular mechanisms of muscle contraction.
Challenges classical kinetics for actomyosin ATPase; leaves open aggregation-resistant methods to study cardiac contraction mechanisms.
The energy for muscle contraction is derived from the hydrolysis of ATP, and one of the principal properties of the contractile proteins in vitro is the marked activation of the myosin ATPase by actin at low ionic strength in the presence of magnesium. Since ATP hydrolysis, unlike contraction, can be quantitatively measured in a homogeneous system of purified proteins, the study of ATPase kinetics constitutes one of the principal approaches to the molecular mechanism of muscle contraction. It is difficult to apply the classical methods of steady state enzyme kinetics to the actomyosin ATPase, however, because the conditions necessary for the actin-activated ATPase also cause aggregation of myosin into filaments and precipitation of actomyosin. If simple mass-action kinetics are to be applied to the actin-myosin interaction, at least one of the proteins must be present in solution as separate molecules which can react independently with the active sites of the...
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Carl Moos (1973) studied this question. Actin was evaluated on ATPase kinetics. Classical steady state enzyme kinetics are difficult to apply to actomyosin ATPase because the conditions required for actin activation cause myosin aggregation and actomyosin precipitation.
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