Related Experiment Video
Updated: Jun 4, 2026

The Importance of Correct Protein Concentration for Kinetics and Affinity Determination in Structure-function Analysis
Published on: March 17, 2010
α1-Antichymotrypsin inactivates staphylococcal cysteine protease in cross-class inhibition
Benedykt Wladyka1, Agata J Kozik, Michal Bukowski
1Department of Analytical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland. wladykab@interia.pl
Abstract:
Staphylococcal cysteine proteases are implicated as virulence factors in human and avian infections. Human strains of Staphylococcus aureus secrete two cysteine proteases (staphopains A and B), whereas avian strains express staphopain C (ScpA2), which is distinct from both human homologues. Here, we describe probable reasons why the horizontal transfer of a plasmid encoding staphopain C between avian and human strains has never been observed. The human plasma serine protease inhibitor α(1)-antichymotrypsin (ACHT) inhibits ScpA2. Together with the lack of ScpA2 inhibition by chicken plasma, these data may explain the exclusively avian occurrence of ScpA2. We also clarify the mechanistic details of this unusual cross-class inhibition. Analysis of mutated ACHT variants revealed that the cleavage of the Leu383-Ser384 peptide bond results in ScpA2 inhibition, whereas hydrolysis of the preceding peptide bond leads to ACHT inactivation. This evidence is consistent with the suicide-substrate-like mechanism of inhibition.
More Related Videos
Related Concept Videos
Clinical Significance of Antibiotic Resistance
Staphylococcal Skin Infections
Indirect-Acting Cholinergic Agonists: Mechanism of Action
Reversible inhibitors like edrophonium bind to a specific part of the enzyme called the anionic catalytic site. They form noncovalent bonds, which means they are not strongly attached to the enzyme. This creates a temporary and less stable enzyme–inhibitor complex, leading to...
Inhibitors of Bacterial Protein Synthesis
Allosteric Proteins-ATCase
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Mechanism of Antibiotic Resistance in MRSA

