Matrix-targeting sequences

Located at the N-terminus

Usually 20–50 amino acids in length

Rich in hydrophobic amino acids, positively charged basic amino acids (arginine & lysine), and hydroxylated ones (serine and threonine)

Amphipathicity of matrix-targeting sequences is critical to their function

TLS Online TPP Program

#Id: 8198

#Unit 2. Cellular Organization

Lysosomes are membrane-enclosed organelles filled with soluble hydrolytic enzymes that digest macromolecules.

TLS Online TPP Program

#Id: 8199

#Unit 2. Cellular Organization

Lysosomes contain about 40 types of hydrolytic enzymes, All are acid hydrolases, work best at acidic pH including: proteases, nucleases, glycosidases, lipases, phospholipases, phosphatases, and sulfatases.

TLS Online TPP Program

#Id: 8200

#Unit 2. Cellular Organization

For optimal activity, of acid hydrolases they need to be: Activated by proteolytic cleavage Requires an acid environment.

TLS Online TPP Program

#Id: 8201

#Unit 2. Cellular Organization

Lysosome an interior pH of about 4.5–5.0

TLS Online TPP Program

#Id: 8202

#Unit 2. Cellular Organization

Most of the lysosome membrane proteins, are highly glycosylated, which helps to protect them from the lysosome proteases

TLS Online TPP Program

#Id: 8203

#Unit 2. Cellular Organization

An H+ ATPase in the membrane pumps H+ into the lysosome, maintaining its lumen at an acidic pH.