A bacterial type II enzyme, called either topoisomerase II or DNA gyrase, can introduce negative supercoils (decrease Lk). It uses the energy of ATP to accomplish this.

To alter DNA linking number, type II topoisomerases cleave both strands of a DNA molecule and pass another duplex through the break.

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.

TLS Online TPP Program

#Id: 8204

#Unit 2. Cellular Organization

Lysosome H+ pump are V-type ATPases and has a similar architecture to the F-type ATPases