Enzymes and Cofactors Overview

Enzymes and Cofactors

• Enzymes are biological catalysts that speed up biochemical reactions without being consumed in the process.
• Enzymes have a specific active site that binds to a substrate, forming an enzyme-substrate complex.
• The enzyme then catalyzes the reaction, converting the substrate to a product, which is then released.
• Holoenzyme is the complete, active enzyme.
• Apoenzyme is the protein portion of the enzyme, and needs a cofactor to be active.

Cofactors

• Cofactors are non-protein molecules that assist enzymes in their catalytic activity.
• Cofactors may be inorganic ions (like metal ions) or organic molecules (like coenzymes).
• Coenzymes are organic molecules that help enzymes catalyze reactions.
• Coenzymes are often derived from vitamins.
• Prosthetic groups are tightly bound cofactors that are permanently associated with the enzyme.

Classification of Cofactors

• Inorganic ions: Ions such as zinc ions, chloride and calcium.
• Organic molecules: Coenzymes are organic molecules that are derived from vitamins, such as vitamin B3 and B5.
• Prosthetic groups: Tightly bound cofactors are permanently associated with the enzyme. These include transition metals such as zinc.

Roles of Cofactors

• Cofactors help enzymes to achieve their optimum activity in reactions.
• Some cofactors (like chloride ions) help determine the shape of the active site of the enzyme to allow for substrate binding.
• Other cofactors (like coenzyme A) participate in the reaction mechanism itself, assisting in the transformation of the substrate to the product.

Inactive precursor enzymes (zymogens)

• Some enzymes are produced in an inactive form called zymogens.
• Zymogens need to be activated by a certain process (chemical cleavage) to become active enzymes.
• This activation process is important in regulating enzyme activity and preventing unintended reactions.
• Inactive or precursor enzymes do not cause damage to cells.

This quiz delves into the intricate roles of enzymes and cofactors, exploring how enzymes act as biological catalysts and the necessity of cofactors for their function. Understand the distinctions between holoenzymes, apoenzymes, inorganic ions, and coenzymes, and gain insights into enzymatic activity. Test your knowledge on these fundamental biological concepts.