BCH210H1 Lecture Notes - Lecture 10: Oxaloacetic Acid, Flavin Mononucleotide, Porphyrin

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BCH210H1 Full Course Notes

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Cofactors required to convert inactive enzymes (apoenzymes) to active (holoenzymes) Cofactors include: essential ions (metal, organic compounds coenzymes. Activator ions reversibly bound and often participate in binding substrates. Metal ions of metalloenzymes some cations are tightly bound and participate directly in catalytic reactions. Cosubstrates specific for chemical groups that accept and donate: hydrogen or electron. Prosthetic groups large groups covalently attached at reactive centre: can be derived from vitamins. > 25% known enzymes require metallic cations for full catalytic function: metal-activated enzymes have an absolute requirement for added metal ions or alternatively are stimulated by addition of metal ions. Monovalent cations/divalent cations (e. g. k+, ca2+, mg2+) Usually transition metals: iron and zinc, and sometimes copper and cobalt. E. g. cofactor for carbonic anhydrase (reaction of water and carbon dioxide end product of aerobic respiration) is an electrophilic zn2+ atom bound to the side chains of 3 histidine (imidazole rings) residues and a molecule of water.

Related Questions

Which statement expresses the correct relationship between cosubstrates, coenzymes, and cofactors? A)Coenzymes are cosubstrates that transiently bind to enzymes, while coenzymes are cofactors that are organic compounds. B)Cosubstrates are coenzymes that transiently bind to enzymes, while cofactors are coenzymes that are organic compounds. C)Coenzymes are cosubstrates that transiently bind to enzymes, while cofactors are coenzymes that are organic compounds. D)Cosubstrates are coenzymes that transiently bind to enzymes, while coenzymes are cofactors that are organic compounds.

What is NOT a function or characteristic of cofactors or coenzymes?

	1.	Electron carriers can serve as coenzymes
	2.	Most protein enzymes are cofactors
	3.	Most vitamins are coenzymes
	4.	Metal ions can be cofactors that are required in tiny amounts
	5.	ATP acts as one by donating phosphate groups

emeraldturtle80

Pyruvate dehydrogenase is a large, highly integrated complex containing many copies of three distinct enzymes. There are five coenzymes involved in its catalytic activity: NAD , FAD, coenzyme A, lipoamide, and thiamine pyrophosphate (TPP or TDP). The coenzymes can be classified depending on how they participate in an enzymatic reaction.

A coenzyme prosthetic group is tightly bound to the enzyme and remains bound during the catalytic cycle.

The original coenzymes are regenerated during the catalytic cycle.

On the other hand, a coenzyme cosubstrate is loosely bound to an enzyme and dissociates in an altered form as part of the catalytic cycle. Its original form is regenerated not by the cycle, but by another enzyme.

BCH210H1 Lecture Notes - Lecture 10: Oxaloacetic Acid, Flavin Mononucleotide, Porphyrin

BCH210H1 Full Course Notes

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