Cofactors: Inorganic substances like metal ions that are required to increase the rate of catalysis. Chemical compunds or elements associated with the enzyme to increase its efficiency. There are mainly two types- inorganic ions and organic compounds. Inorganic ions: Known as enzyme activators (Cl ion in salivary amylase). Organic compunds: Divided into two types- co-enzymes and prosthetic groups.

cofactorenzyme or protein Zn++ carbonic anhydrase, alcohol dehydrogenase Fe+++ or Fe++ cytochromes, hemoglobin, ferredoxin Cu++ or Cu+ cytochrome oxidase K+ and Mg++ pyruvate phosphokinase

Coenzymes: Cofactors that are bound to an enzyme loosely. Non protein organic/ metallo organic molecules. Non covalently/covalently attached to the enzyme. Special case of cofactors. (With Prosthetic groups) Can be removed from the enzyme & undergo cyclic reactions to combine with enzyme (EX: NAD, NADP)

VITAMIN COENZYMERxN MEDIATED NIACIN nicotine adenine dinucleotide, nicotine adenine dinucelotide phosphate (NADH,NADHP-Partly composed of niacin) OXIDATION-REDUCTION RxN electron (hydrogen atom) transfer RIBOFLAVIN (VITAMIN B2) flavine adenine dinucleotide(FADH,FAD+ Partly composed of riboflavin - vit. B2) OXIDATION-REDUCTION RxN electron (hydrogen atom) transfer PANTOTHENATE (PANTOTHENIC ACID) coenzyme AAcyl groups activation & transfer Co-Q10coenzymeQ10 OXIDATION-REDUCTION RxN electron (hydrogen atom) transfer THIAMINE (VITAMIN B1) thiamine pyrophosphate Activation & transfer of aldehydes (carbonyl groups) PYRIDOXINE (VITAMIN B6) pyridoxal phosphateAmino acids activation & amino groups transfer

VITAMINCOENZYMERxN MEDIATED COBALAMIN (VITAMIN B12) Carbamide coenzymesAlkyl groups / alkylation RxN (Isomerization & Methyl group transfer) BIOTINbiotinCARBOXYLATION RxN (carbon dioxide activation & transfer) NICOTINAMIDEnicotinamideOXIDATION-REDUCTION RxN electron (hydrogen atom) transfer FOLIC ACIDtetrahydrofolateActivation & transfer of single carbon groups. LIPOIC ACIDlipoamideAcylgroup activation & transfer OXIDATION-REDUCTION RxN

CofactorCoenzyme DefinitionIt is a non-protein chemical compounds that are bound tightly or loosely to an enzyme or other protein molecules. It is defined as small, organic, non-protein molecules, which carry chemical groups between enzymes. Molecule typeThese are organic as well as inorganic compounds / substances. These are organic molecules / substances. FunctionIt assists in biological transformations. It aids or helps the function of an enzyme or the relative enzyme. TypeThey are chemical compounds. Two types of cofactors are: coenzymes & prosthetic groups. They are chemical molecules, include under type of cofactor.

CofactorCoenzyme Binding strength It is loosely or tightly bound that is covalently bound to an enzyme. It is loosely bound to an enzyme. ActionThey act on catalyst to increase the speed of the reaction. They act as carries to the enzymes. RoleThey increase the rate of the reaction that is catalyzed by the relevant enzyme. They serve as carriers to the enzymes. RemovalThey can only be removed by denaturing the enzyme. They can be removed from the enzyme easily since they are loosely bound to the enzyme.

CofactorCoenzyme CharacteristicIts presence is important for the activity of an enzyme. They bind with an enzyme to catalyze a reaction. ExampleMetal Ions like Zn++, K+ and Mg++, etc. Vitamins, Biotin, Coenzyme A, etc

TERMINOLOGY PROSTHETIC GROUPS Co factors /co enzymes that are tightly bound to the enzyme molecules(EX : FAD). TURNOVER RATE The number of substrate molecules acted upon by an enzyme in one second under appropriate conditions. INTERNATIONAL UNIT Amount of enzyme causing Transformation of 1μmol of substrate/minute under optimal conditions. APOENZYME Protein component of enzyme. HOLOENZYME Apoenzyme + non protein component.

TERMINOLOGY ACTIVE SITE Special pocket or cleft in an enzyme molecule. Has amino acid side chains for substrate binding &catalysis. ALLOSTERIC SITES Enzymes have allosteric sites(other than active site) where effectors (chemical reagents acting as modifiers) bindthrough non covalent linkage. ACTIVITY Total units of enzymes in a given solution. SPECIFIC ACTIVITY Number of enzyme units/mg of total protein. KATAL Amount of an enzyme which catalyzes a reaction rate of 1 mole of substrate / second. SUBSTRATE The substance upon which an enzyme acts is called the substrate.

Reference: 1. Helmenstine, Ph.D. Anne Marie. “What Is a Coenzyme? Definition and Examples.” ThoughtCo. N.p., n.d.. 2. “Cofactor.” Encyclopædia Britannica. Encyclopædia Britannica, inc., n.d. Web.. 3. “Coenzymes and cofactors.” Coenzymes and cofactors. N.p., n.d. Web.. 4. J.H. Freeland-Graves, C. Bavik, in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003

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