What are cysteine proteases?

Question

I understand that proteases break down polypetides, but what exactly do cysteine proteases do? I am trying to research apoptosis (programmed cell death), and this word came up, and I'm not sure what it means. Information I found on Google was too advanced for me to understand. So, can you try to explain this in basic terms? Thank you.

Answer 1

cysteine proteases have a free cysteine at their active site  that participates in their ability to degrade certain proteins ( proteolytic actiivty. Cysteine proteases such as papain and cathepsins work at lower pHs than the serine proteases like trypsin and chymotrypsin. In lysosomes and phagolysosomes proteins are degraded at pH ~ 5-5.8  which overlaps the pH range for cysteine proteases, such as cathepsins. In the small intestine and in plasma where the pH is higher ----7.1-8.2 ( intest)  then cysteine proteases are not active and serine proteases must degrade the proteins

Answer 2

Proteases are enzymes that degrade polypeptides and proteins. Cysteine proteases have a common catalytic mechanism that involves the amino acid cysteine in its active site.