1Proteasespeptidases are found in a variety of locations in

1.Proteases/peptidases are found in a variety of locations in the body. Proteases are hydrolases enzymes that catalyse the breaking of peptide bonds. Blood has a pH of 7.4, cytoplasm a pH of 7.2, the inside of a lysosome a pH of 5.0, the stomach has a pH of 2.3. I have just discovered a new protease.If I want to check using experiments at the lab bench whether my protein can work in the stomach? Which acid will be the basis of my buffer?

H₂PO₄^-

H₃PO₄

HPO₄^2-

NH₄⁺

CH₃COOH

HCl

2.My colleague has found that mice deficient in my protease are more susceptible to invasion by certain classes of bacteria. I also know that infected cells die by commiting suicide using proteases. Which acid should my buffer be based upon for my enzyme to work in if it is involved in PCD/apoptosis?

H₂PO₄^-

HCl

CH₃COOH

NH₄⁺

H₃PO₄

HPO₄^2-

3.I do not see extra cell death. So...I also know that there are two types of lysosomes. One type of lysosome recycles materials from within the cell, materials brought in from outside the cells, and phagocytosed invaders. The second class are loaded with enzymes that are inactive in the lysosome, but active at the pH of blood. These lysosomes are targeted to invaders on the outside of cells that either cannot/are not/ or have not been phagocytosed. The fusion of these lysosomes with the cell membrane acts as a warhead releasing proteins that attack the adjacent invader.I think my protease is a part of this \"warhead\" lysosome. In a buffer made from which acid should my protease work?

H₂PO₄^-

NH₄⁺

H₃PO₄

HCl

CH₃COOH

HPO₄^2-

4.My protease appears to affect bacteria, but not my own cells. What type of peptides/proteins might my protease hydrolyze/cut? Pick ALL that apply.

peptidoglycans

glycoproteins

lipoproteins

porins

transporters

metalloproteins

Solution

1. To check efficiency of protease in stomach, hydrochloric acid (HCl) is the choice of acid to be used in the buffer because stomach contains HCl. Option F is correct.

2. Mouse cells invaded by bacteria undergo apoptosis or suicide or self death. These cells are degraded by lysosomal enzymes. The proteases to be used in lysosomes need a buffer containing acetic acid (CH₃COOH). This is because, the pH of acetic acid is near to pH of lysosomes. Option C is correct.

3. The pH of blood is 7.35. The blood pH is maintained by phosphoric and carbonic acids. The fuction of protease in blood is performed efficiently when the protease works in a buffer containing HPO_4^2- or phosphoric acid. Option F is correct.

4. The proteases affecting bacteria may hydrolyze structures like peptidoglycan, surface glycoprroteins, lipoproteins, porins and transporter proteins that exist in cell membrane of bacteria. Options A, B, C, D and E are correct.