Chemical Modifications on Proteins Using Glutaraldehyde

Carla J. S. M. Silva¹, Fernanda Sousa¹, Georg Gübitz² and Artur Cavaco-Paulo¹*

¹Department of Textile Engineering/Minho University, Guimarães, Portugal
²Department of Environmental Biotechnology, Graz University of Technology, Graz, Austria

Article history:
Received: September 22, 2003
Accepted: February 16, 2004

Key words:
protease, proteins, crosslinking, glutaraldehyde, chromatography, SDS-PAGE

Summary:
In this work the effect of crosslinking the enzyme esperase (E.C. 3.4.21.62) and the proteins bovine serum albumin and casein with the bifunctional compound glutaraldehyde on molecular mass increase was studied. Two common techniques for measuring molecular mass of proteins were used: SEC and SDS-PAGE. These techniques revealed that the proteins bovine albumin and casein, when subjected to chemical crosslinking with glutaraldehyde, volume fraction 0.25 %, increased their molecular mass by 20- and 40-fold, respectively. It was also observed that Mr increased proportionally to the increase of glutaraldehyde concentration in the solution, and that the addition of glutaraldehyde should be done slowly, in small amounts, in order to attain bigger protein aggregates. When the proteolytic enzyme esperase was subjected to glutaraldehyde, no increase in its Mr was achieved. Several assumptions can be made to explain these results, the most reasonable being the low amount of free lysine groups available for crosslinking. This study confirms that glutaraldehyde is not an adequate crosslinker for esperase. 

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