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

Purified (Na+, K+)-activated adenosine triphosphatase ((Na+, K+)-ATPase, ATP phosphohydrolase, EC 3.6.1.3) has been subjected to trypsin and chymotrypsin hydrolysis. The glycoprotein is much more resistant to proteolysis than the large chain. This differential susceptibility to proteolysis is not due to differences in the number of trypsin or chymotrypsin sensitive bonds because the two subunits are equally susceptible to proteolysis after isolation by preparative gel electrophoresis in sodium dodecyl sulfate. It is also not due to steric "shielding" of the glycoprotein by the large chain or its proteolytic products: (1) The rate of digestion of the glycoprotein is not increased after 90% of the large chain is digested. (2) The majority of the large chain peptides are released into the supernatant upon degradation. It is concluded that the greater resistance of the glycoprotein to proteolysis is due to its native conformation. In the absence of the large chain, the susceptibility of the glycoprotein to tryptic degradation by K+ and Na+. The evidence suggests that this decreased susceptibility was due to conformational changes in the glycoprotein. These specific ligand effects on proteolysis of the glycoprotein suggests that the glycoprotein may participate in Na+ and K+ binding by (Na+, K+)-ATPase.
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PMID:The susceptibility of the glycoprotein from the purified (Na+, K+)-activated adenosine triphosphatase to tryptic and chymotryptic degradation with and without Na+ and K+. 13 66

Actin can be cleaved by trypsin or chymotrypsin into a large, autonomous fragment with approximately 80% of the mass of the undegraded polypeptide. The protease-resistant cores obtained with either enzyme are very similar. Although the fragment does not bind calcium ions and fails to polymerize to the filamentous form of actin or to stimulate myosin adenosine triphosphatase (ATP phosphohydrolase, EC 3.6.1.3) activity, it retains the full capacity to bind ATP. This observation suggests that it represents an independent functional unit. Cleavage of globular actin with either trypsin or chymotrypsin occurs with half-times of 3 min, while that of filamentous actin proceeds with reaction half-times of 20 min for trypsin and nearly 2 hr for chymotrypsin. Denaturation and renaturation of the trypsin-resistant core shows that approximately 20% of the molecules refold to functional forms which indicates that the fragment can be considered as an independent unit of folding as well.
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PMID:ATP binding to a protease-resistant core of actin. 13 74