Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The orientation of the condensing enzyme, the beta-hydroxyacyl-CoA dehydrase, and the trans-2-enoyl CoA reductase within the rat liver microsomal membrane was investigated by the use of impermeant inhibitors of enzyme activity: trypsin, chymotrypsin, subtilisin, mercury-dextran, and anti-beta-hydroxyacyl-CoA dehydrase IgG. The activity of the condensing enzyme was inhibited more than 70% by various proteases and was completely inhibited by 80 microM mercury-dextran. Similar results were obtained for the trans-2-enoyl-CoA reductase activity. On the other hand, in the absence of detergent, proteases inhibited beta-hydroxyacyl-CoA dehydrase activity by 25-40%, while in the presence of detergent the inhibition increased to 65-90%. Furthermore, anti-beta-hydroxyacyl-CoA dehydrase IgG, which in the absence of detergent produced no inhibition, in the presence of detergent inhibited beta-hydroxyacyl-CoA dehydrase activity by more than 80%; under identical conditions, preimmune IgG caused a 13% inhibition. Microsomes used throughout this study displayed greater than 90% latency with respect to mannose-6-phosphatase activity, indicating that the microsomes were intact. Latency was not affected by the proteases, by mercury-dextran, or by the presence of the enzyme assay components. These results suggest that both the condensing enzyme and the reductase are present on the cytoplasmic surface of the membrane, whereas the beta-hydroxyacyl-CoA dehydrase is embedded in the microsomal membrane.
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PMID:Topography of rat hepatic microsomal enzymatic components of the fatty acid chain elongation system. 254 Jan 64

Chicken fatty acid synthetase is cleaved by alpha-chymotrypsin into two fragments of molecular weight 230,000 and 33,000. These fragments may be easily separated by ammonium sulfate fractionation and gel filtration to yield pure preparations. The large 230,000-Da fragment contains all of the core activities of the fatty acid synthetic sequence i.e. acetyl and malonyl transacylases, condensing enzyme, beta-ketoacyl and enoyl reductases, the dehydratase, and the acyl carrier protein. The smaller 33,000-Da fragment retains the thioesterase activity which catalyzes the release of the completed acyl chains from the complex. Antibodies against the purified thioesterase fragment cross-react with analogous (Mr 33,000) peptides released from the complex by other proteases, as well as with all proteolytic intermediates that were predicted by peptide mapping to contain the thioesterase segment (Mattick, J. S., Tsukamoto, Y., Nickless, J., and Wakil, S. J. (1983) J. Biol. Chem. 258, 15291-15299). Amino acid sequence analyses demonstrate that the thioesterase domain is located at the carboxyl terminus of the synthetase monomer, thereby orienting the proteolytic (and functional) sites within the complex with respect to the direction of transcription and translation.
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PMID:The architecture of the animal fatty acid synthetase. II. Separation of the core and thioesterase functions and determination of the N-C orientation of the subunit. 665 13