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Enhanced activity of immobilized pepsin nanoparticles coated on solid substrates compared to free pepsin

Paper ID Volume ID Publish Year Pages File Format Full-Text
17120 42643 2014 10 PDF Available
Title
Enhanced activity of immobilized pepsin nanoparticles coated on solid substrates compared to free pepsin
Abstract

•Pepsin nanoparticles (NPs) are formed in an aqueous buffer solution of pepsin.•The pepsin NPs were immobilized on polyethylene film, polycarbonate and glass.•The immobilization of the NPs on the solid supports was done sonochemically.•The activity of free enzyme was compared to the activity of the immobilized enzymes.

In the present work nanoparticles (NPs) of pepsin were generated in an aqueous solution using high-intensity ultrasound, and were subsequently immobilized on low-density polyethylene (PE) films, or on polycarbonate (PC) plates, or on microscope glass slides. The pepsin NPs coated on the solid surfaces have been characterized by HRSEM, TEM, FTIR, XPS and DLS. The amount of enzyme introduced on the substrates, the leaching properties, and the catalytic activity of the immobilized enzyme on the three surfaces are compared. Catalytic activities of pepsin deposited onto the three solid surfaces as well as free pepsin, without sonication, and free pepsin NPs were compared at various pH levels and temperatures using a hemoglobin assay. Compared to native pepsin, pepsin coated onto PE showed the best catalytic activity in all the examined parameters. Pepsin immobilized on glass exhibited better activity than the native enzyme, especially at high temperatures. Enzyme activity of pepsin immobilized on PC was no better than native enzyme activity at all temperatures at pH 2, and only over a narrow pH range at 37 °C was the activity improved over the native enzyme. A remarkable observation is that immobilized pepsin on all the surfaces was still active to some extent even at pH 7, while free pepsin was completely inactive. The kinetic parameters, Km and Vmax were also calculated and compared for all the samples. Relative to the free enzyme, pepsin coated PE showed the greatest improvement in kinetic parameters (Km = 15 g/L, Vmax = 719 U/mg versus Km = 12.6 g/L and Vmax = 787 U/mg, respectively), whereas pepsin coated on PC exhibited the most unfavorable kinetic parameters (Km = 18 g/L, Vmax = 685 U/mg). The values for the anchored enzyme-glass were Km = 19 g/L, Vmax = 763 U/mg.

Keywords
Sonochemistry; Pepsin nanoparticles; Immobilization; Enzyme activity; Enzyme kinetics; Retention
First Page Preview
Enhanced activity of immobilized pepsin nanoparticles coated on solid substrates compared to free pepsin
Publisher
Database: Elsevier - ScienceDirect
Journal: Enzyme and Microbial Technology - Volume 67, December 2014, Pages 67–76
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering