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1 year ago in Enzymology , Microbiology By Rahul K
Is there a method to detect extracellular proteases by color change?
I'm screening a library of environmental isolates for extracellular protease activity, a key virulence factor for some pathogens. Spectrophotometric assays are precise but low-throughput for initial screening. I need a solid or liquid medium where a clear color change indicates hydrolysis, allowing me to quickly identify positive hits for further study.
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By Rajesh Gundlapalli Answered 1 year ago
From my experience in microbial physiology, the most straightforward method is still the casein hydrolysis plate. You incorporate skim milk (a source of casein) into an agar medium. After incubating your isolates, a clear halo around the colony indicates protease secretion the casein is hydrolyzed and no longer scatters light. For a more quantitative color change in liquid culture, I would recommend using a substrate like azocasein. Upon protease activity, it releases soluble orange-red peptides that you can measure spectrophotometrically after precipitating the unhydrolyzed protein. This gives you both a visual and numeric readout.
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