MadSci Network: Biochemistry
Query:

Re: How can I test the enzyme effectiveness of papain (papaya extract)?

Area: Biochemistry
Posted By: Michael Onken, WashU
Date: Mon Jun 9 17:05:12 1997
Area of science: Biochemistry
ID: 861300598.Bc
Message:

Papain (pictured here) is a proteolytic enzyme which breaks proteins into smaller fragments, usually neutralizing their activities and aiding in their digestion. Papain is easily isolated from the latex of the Papaya, making it commercially available as a broad spectrum protease. Because of the importance of prot eases in biology, several kits are available from various companies for the det ection of protease activity in samples. All of these kits are expensive, and require laboratory equipment to run, so they are not much use to the home scientist.

Fortunately, there is a protocol that is used by biochemists studying the activities of proteases. The most commonly available substrate for papain is gelatin. But, gelatin desserts can be unruly as a source of substrate (besides which Grad Students are like vultures, and a bowl of Jell-O wouldn't last five minutes in the lab), so an alternative source of gelatin is used. Luckily, photographic film (we use X-ray film) is composed of a plastic backing covered with an emulsion of light-sensitive chemicals in gelatin. So film is the perfect material for testing the activity of proteases.

Just make solutions of the papains you want to test, and place a drop of each onto the emulsion side of some photographic film (you might try using some slides that you don't want, since they are already individually wrapped), wait a few minutes for the e nzymes to work, rinse off the samples, dry the film, and see which samples leave the clearest holes in the emulsion. You may have to optimize the conditions with some papain that you know is good (for a positive control), before you get an accurate readi ng of the unknown samples, and it would be a good idea to include a sample without papain (for a negative control) to be sure that you're not just scoring water spots. This technique worked for us in the lab, although we were testing for proteases unrela ted to papain.


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