Effect of alkylamine on activity and stability of immobilized angiotensin converting enzyme

Angiotensin converting enzyme (ACE) was immobilized on chitosan microspheres with glutaraldehyde as cross-linking reagent. The activity and stability of immobilized ACE (I-ACE) were improved by further modification with alkylamines. The modification conditions were optimized. The characteristics of I-ACE and modified I-ACE (MI-ACE) including activity, kinetic parameters, optimal pH and temperature, stability and reusability were investigated. After modification, I-ACE activity was increased, Km decreased from 4.33 mM to 2.61 mM, optimal pH value was altered, pH stability, storage stability and thermal stability were improved, and optimal temperature did not change.

Effect of concentrations of methylamine, n-butylamine and ethanolamine on the activity of immobilized ACE. (The solutions were prepared with water, pH 8.3, adjusted by HCl.)The activity of immobilized ACE (I-ACE) could be improved significantly after modification. Methylamine, n-butylamine and ethanolamine exhibited activation in a broad concentration range. After modifying under the optimum condition (2240 mM methylamine), the activity of the modified I-ACE was 2 folds higher than that of I-ACE.Figure optionsDownload as PowerPoint slideHighlights
► ACE was immobilized on chitosan microspheres with glutaraldehyde.
► The modification aiming at quenching excess aldehyde groups in immobilized ACE.
► The activity and stability of immobilized ACE were improved by modification.
► The modification can be used to recover I-ACE activity after storage.