Abstract
The amidolytic activity of chymotrypsin for Suc-Ala2-Pro-Phe-MCA was somewhat enhanced by dimyristoyl PC at low ionic strength, but not at high ionic strength. The activity was strongly inhibited by pure egg yolk PA. The inhibition by 200 ng PA was neutralized by addition of 1 μg dimyristoyl PC or pure egg yolk PC, which formed vesicles with the PA. The Km and kcat (s−1) values of chymotrypsin for hydrolysis of Suc-Ala2-Pro-Phe-MCA changed from 15 μM to 42 μM, 0.1 idm and 0.5 μM, and from 1.5 to 2.7, 3.7, and 1.0 in the presence of 1 μg dimyristoyl PC, 0.5 μg pure egg yolk PE and 0.2 μg egg yolk PA, respectively. Gel-filtration chromatography showed that dimyristoyl PC formed a complex with chymotrypsin, but did not interact with the substrate, indicating that the basic globular protein, chymotrypsin, interacted with net-neutral PL.

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