Proenzyme

Proenzyme

A proenzyme is an inactive precursor of an enzyme. The body produces proenzymes, which are then activated when needed. This process allows the body to control the activity of certain enzymes and prevent them from breaking down proteins that are not meant to be broken down.

Structure

Proenzymes are structurally different from their active counterparts. They often have an extra protein sequence, known as a propeptide, which prevents the enzyme from becoming active. The propeptide must be removed or altered for the enzyme to become active.

Activation

The activation of a proenzyme can occur in several ways. Some proenzymes are activated by other enzymes, which cleave the propeptide and allow the enzyme to become active. Others are activated by changes in pH or temperature.

Examples

There are many examples of proenzymes in the human body. For example, pepsinogen is a proenzyme that is converted into the active enzyme pepsin in the stomach. Similarly, trypsinogen is a proenzyme that is converted into trypsin in the small intestine.

Clinical significance

Proenzymes have important clinical significance. For example, the levels of certain proenzymes in the blood can be used as markers for certain diseases. In addition, some drugs work by inhibiting the activation of certain proenzymes.

See also

• Zymogen
• Enzyme
• Pepsinogen
• Trypsinogen

References

Proenzyme Resources
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