ISSN:
1573-2657
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The effects of both the P 3-1-(2-nitrophenyl)ethyl ester of adenosine 5′-triphosphate (NPE-caged ATP) and its separate diastereoisomers, and the P 3-3′,5′-dimethoxybenzoin ester of ATP (DMB-caged ATP) were studied on the unloaded shortening velocity of glycerinated rabbit psoas muscle fibres. The unloaded shortening velocities of the active fibres were measured as a function of ATP concentration (0.1–5 mm) using the ‘slack-test’ with and without 2 mm caged ATP. Shortening velocity followed a Michaelis-Menten relationship with ATP concentration, the Km for ATP being 170 μm. The caged ATP compounds inhibited shortening velocity, in a manner consistent with competitive inhibition, with a Ki of 1–2 mm. The R- and S-diastereoisomers of NPE-caged ATP showed the same degree of competitive inhibition of the shortening velocity, as did DMB-caged ATP. These observations suggest that caged ATP compounds bind to the ATPase site of the actomyosin where they compete with the substrate, Mg2+ATP.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00122531
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