Definitions and types of coenzymes

Coenzyme - Introduction, Definition, Examples for coenzyme, reaction catalysed by coenzyme, Types of coenzymes - cosubstrate and prosthetic group coenzymes, second type of classification of coenzyme- hydrogen group transfer , other than hydrogen group transfer.

1. Definitions and types of Coenzymes Jasmine Juliet .R Biochemistry Agricultural College & Research Institute, Madurai.

2. Coenzyme - Introduction An enzyme is a protein that functions as a catalyst to mediate and speed a chemical reaction. Coenzyme is  a substance that enhances the action of an enzyme .  The catalytic activity of enzymes mostly depends on the presence of non-protein compounds called coenzymes . coenzymes cannot be isolated from apoenzymes without denaturation of the enzyme proteins.

3. Coenzyme - Introduction Coenzymes are small molecules . They cannot by themselves catalyze a reaction but they can help enzymes to do so. In technical terms, coenzymes are organic nonprotein molecules that bind with the protein molecule ( apoenzyme ) to form the active enzyme ( holoenzyme ) . A number of the water-soluble vitamins such as  vitamins B1, B2 and B6 serve as coenzymes .

4. Coenzyme - Definition   Coenzyme (Biology definition): Molecule required by a particular enzyme to carry out catalysis of a chemical reaction is called as coenzyme. Examples of coenzymes:   nicotineamideadenine dinucleotide  (NAD),  nicotineamide adenine dinucelotide ph osphate  (NADP), and   flavin adenine dinucleotide  (FAD). These three coenzymes are involved in oxidation or hydrogen transfer.

5. Coenzyme

6. Example for coenzyme: Succinate dehydrogenase catalysed reaction. FAD act as coenzyme.

7. Water-Soluble Vitamins Coenzyme Coenzyme  Function vitamin B 1 (thiamine) thiamine pyrophosphate decarboxylation reactions vitamin B 2 (riboflavin) FMN oxidation-reduction vitamin B 3 (niacin) NAD / NADP oxidation-reduction vitamin B 6 (pyridoxine) pyridoxal phosphate transfer of amino groups vitamin B 12 (cyanocobalamin) methylcobalamin or deoxyadenoxylcobalamin rearrangement reactions biotin biotin carboxylation reactions folic acid tetrahydrofolate carrier of one-carbon units pantothenic Acid coenzyme A carrier of acyl groups

8. Coenzyme - Types Cosubstrate (loosely bound): A coenzyme substrate is loosely bound to an enzyme and dissociates in an altered form as part of the catalytic cycle. Examples: ATP S- Adenosyl Methionine Uridine Di Phosphate-sugar NAD+/NADP+ Ttetrahydrofolate CoA ubiquinone protein coenzymes

9. I. Cosubstrate coenzyme (NAD)

10. Coenzyme - Types II. Prosthetic group(tightly bound): A coenzyme prosthetic group is tightly bound to the enzyme and remains bound during the catalytic cycle. A coenzyme that is tightly or even covalently, and permanently bound to a protein. Both prosthetic groups and cosubstrates have the same function, which is to facilitate the reaction of enzymes and proteins. Example: * FMN/FAD * Thiamine Pyro Phosphate * Pyridoxal Phosphate * Biotin * adenosyl / methylcobalamin * Lipoic acid/ lipoamide

11. II. Prosthetic group coenzyme(TPP) e

12. Coenzyme - Types Coenzyme can be classified according to the group transferred . Based on the above concept, we may classify coenzymes as follows: 1 . For transfer of groups other than hydrogen groups. CO-A TPP PLP Biotin 2 . For transfer of hydrogen NAD, NADP FMN, FAD Lipoic acid Coenzyme Q

13. I. Coenzyme - transfer of groups other than hydrogen groups ( Transfer of acyl group)

14. II. Coenzyme - transfer of hydrogen group

15. Coenzyme - Function The coenzyme is essential for the biological activity of the enzyme. A coenzyme is a low molecular weight organic substance , without which the enzyme cannot exhibit any reaction. A coenzymes prepares the active site for catalytic activity. The function of coenzyme is to transfer of groups between enzymes. A coenzyme is necessary helper for enzymes that assist in biochemical transformations. A coenzyme transport a variety of chemical groups ( such as Hydride, Acetyl, Formyl , Methenyl , Methyl)

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