Casein is used as a substrate in enzyme activity tests, and the enzyme is bromel
ID: 700546 • Letter: C
Question
Casein is used as a substrate in enzyme activity tests, and the enzyme is bromelain (in this case).
To quantify the enzyme activity, tyrosine, an amino acid, is used as a reference.
If casein is intact there will be no tyrosine, however, if bromelain has catalytic activity, chains of peptides containing tyrosine will form. From a standard tyrosine titration curve, enzyme activity can be compared. The more tyrosine that is released from casein, the stronger the activity of the protease.
In tube 1, tyrosine is the standard. Trichloroacetic acid is a protein denaturing agent, so when added to tyrosine it has no effect.
In tube 2, the pineapple sample is added, if trichloroacetic acid is added before the enzymatic activity, the bromelain will be denatured and its protease activity would be zero. That is why it is added after the reaction, only to stop the enzyme reaction.
Explanation / Answer
Tube of tyrosine Tube of sampleTube of water (mL) 2.5 (mL) Step 290 Casein in the phosphate buffer (mL) 2.5 2.5 Keep the tubes at 350 C for 5 minutes 5% Trichloroacetic acid 0.2M HC Tyrosin solution 0.5 0.5 0.5 14 Pineapple solution containing bromelain 0.2 0 Shake the tubes well at 35°C for 10 minutes 5% Trichloroacetic acid Pineapple solution containing bromelain 0 0.2 0 0.2