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Biomedical subjects

E Shaw

Publications and source records attributed to E Shaw.

At least 181 records · Page 10Linked to original sources
PubMed1974

Affinity labelling of proteinases with tryptic specificity by peptides with C-terminal lysine chloromethyl ketone.

Methods are described for the synthesis of peptides terminating in Lys-CH(2)Cl. The products were examined as affinity labels for several enzymes of trypsin-like specificity which are resistant to Tos-Lys-CH(2)Cl. In part, the inertness of the latter may be due to the sulphonamide group, since Z-Lys-CH(2)Cl was more effective. However, a number of tripeptides with C-terminal Lys-CH(2)Cl were superior in their ability to inactivate subtilisin, thrombin and plasma kallikrein. The possibility of developing enzyme-specific reagents selective for members within the trypsin-like group is demonstrated by Ala-Phe-Lys-CH(2)Cl, which readily inactivates plasma kallikrein but not thrombin.

Amino Acid Chloromethyl Ketones↗
PubMed1974

13C high-resolution nuclear magnetic resonance studies of enzyme-substrate reactions at equilibrium. Substrate studies of chymotrypsin-N-acetyltyrosine semicarbazide complexes.

N-Acetyl-L-tyrosine semicarbazide is hydrolyzed by chymotrypsin (EC 3.4.21.1) to N-acetyl-L-tyrosine and semicarbazide. If a high concentration of semicarbazide is present, the equilibrium for the reaction can be shifted from hydrolysis to synthesis. Using N-acetyl-L-[(13)C]tyrosine enriched at the carboxyl carbon and high concentrations of semicarbazide hydrochloride, we have studied the enzyme-substrate complex of N-acetyl-L-[(13)C]tyrosine semicarbazide and chymotrypsin A(delta) by (13)C nuclear magnetic resonance. We observe no shift within the experimental accuracy of +/-0.05 ppm as the fraction of substrate bound is changed from 0.17 to 0.70. Since E + S right arrow over left arrow ES is in fast exchange on the nuclear magnetic resonance time scale, it is possible to show that when the substrate is bound to the enzyme in the Michaelis complex, the (13)C resonance is shifted less than 0.1 ppm, indicating that negligible substrate strain occurs in this complex at the site of enzymatic attack. These experiments demonstrate the application of nuclear magnetic resonance to the study of particular states along the reaction pathway for enzyme-substrate reactions at equilibrium.

Carbon Isotopes↗