ISSN:
1573-6881
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Physics
Notes:
Abstract 1. The inhibition of cytochromec oxidase activity by three types of polycation (PL-3, PL-150 or 195, and salmine) § is described for three kinds of oxidase system: dispersed by Tween-80, detergent-free “soluble” oxidase, and particulate oxidase (submitochondrial particles). 2. Salmine acts as a competitive inhibitor towards cytochromec in all three systems, with aK i between 1 and 4μM. PL-3 (low M.W. polylysine) acts as a non-competitive inhibitor of oxidation in all three systems, with aK i of between 10 μM (submitochondrial particles) and 100 μM (detergrent-free oxidase). 3. PL-150 and PL-195, the high M.W. polylysines, act in three distinct ways, depending on the nature of the oxidase preparation: (a) as reversible competitive inhibitors, withK i of about 70 nM (with oxidase dispersed in Tween-80), (b) as stoichiometric inhibitors displaying pseudononcompetivie kinetics (with Keilin-Hartree submitochondrial particles), and (c) as “superstoichiometric” inhibitors, blocking up to 100 equivalents of oxidase, cytochromeaa 3 (with detergent-free oxidase or with cholate-treated submitochondial particles). 4. PL-195 also inhibits NADH and succinate oxidase activities in intact butc-deficient submitochondrial particles; sigmoidal inhibition curves can be observed in such systems. The rate of PL-195 binding was of the order of 106M−1 sec−1 and the true binding constant between 0.1 and 0.01 nM for the systems showing high affinity. 5. High molecular weight polylysines may be useful in investigations of the topology and distribution of cytochromec binding sites on the mitochondrial membrane and in submitochondrial fragments and solubilized preparations. More than one oxidase molecule may be inhibited by one polymer molecule; submitochondrial fragments “opened” by cholate treatment may bind one polymer molecule to several surface sites; Keilin-Hartree particles, with a more “closed” configuration, sesm to bind one polymer molecule to a single site, suggesting a “ecrevice” structure.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01648976
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