Related Experiment Video
Updated: Aug 2, 2026

A Protocol for Functional Assessment of Whole-Protein Saturation Mutagenesis Libraries Utilizing High-Throughput Sequencing
Published on: July 3, 2016
Factors affecting the isopenicillin N synthetase reaction
D Perry1, E P Abraham, J E Baldwin
1Sir William Dunn School of Pathology, University of Oxford, U.K.
Abstract:
1. Isopenicillin N synthetase (IPNS) from Cephalosporium acremonium, which requires Fe2+ and O2 for activity, was highly purified for studies of factors affecting its conversion of delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (LLD-ACV) into isopenicillin N (IPN). EDTA was used to quench the reaction by removal of Fe2+. 2. IPNS was inactivated during the course of the conversion of LLD-ACV into IPN, although it was relatively stable in the absence of LLD-ACV under otherwise similar conditions. In the presence of GSH and ascorbate each IPNS molecule carried out about 200 catalytic events before inactivation, but the turnover number was decreased 5-fold in the absence of ascorbate. 3. After trace metal ions had been removed from IPNS and other components of the reaction mixture by Chelex-100 resin, only about 10 microM-Fe2+ was required for maximum stimulation. Several other transition-metal ions were inhibitors of the enzyme. 4. Both dithiothreitol (DTT) and GSH stimulated IPNS activity, but GSH, unlike DTT, was not rapidly oxidized in the presence of O2 and Fe2+. 5. IPNS was rapidly inhibited by the thiol-blocking reagents N-ethylmaleimide and 2,2'- and 4,4'-dipyridyl disulphide, but not by 5,5'-dithiobis-(2-nitrobenzoic acid) in the same concentration. Inhibition by 2,2'-dipyridyl disulphide could be reversed by DTT.
Related Concept Videos
Introduction to Mechanisms of Enzyme Catalysis
Factors Affecting Protein-Drug Binding: Drug-Related Factors
One crucial factor in drug-protein binding is the drug's lipophilicity or its affinity for fat. More lipophilic drugs tend to have higher binding extents. For example, highly lipophilic drugs like cloxacillin exhibit substantial protein binding, with as much as 95% of the drug binding to proteins. In contrast,...
Production of Antibiotics
Production of Pharmaceuticals
Inhibitors of Gram-positive Cell Wall Synthesis
Inhibitors of Bacterial Protein Synthesis

