Coenzymes coenzyme

Coenzymes Coenzyme A Benzoyl-coenzyme A reductase, acetyl-coenzyme A carboxylase, 3 -methylcrotonyl-coenzyme-A carboxylase... 

Like many vitamins, cobalamin is functionally active as a derived coenzyme, coenzyme B12. Structurally, this is composed of a corrin ring a haem-like porphyrin ring containing cobalt (Co3+) at the centre held by four coordination bonds. The fifth... 

S. Subramanian, J. B. A. Ross, L. Brand, and P. D. Ross, Investigation of the nature of enzyme-coenzyme interactions in binary and ternary complexes of liver alcohol dehydrogenase with coenzymes, coenzyme analogs, and substrate analogs by ultraviolet absorption and phosphorescence spectroscopy, Biochemistry 20, 4086-4093 (1981). 

Two vitamins, nicotinamide and pyridoxine (vitamin B6), are pyridine derivatives. Nicotinamide participates in two coenzymes, coenzyme I (65 R = H) which is known variously as nicotinamide adenine dinucleotide (NAD) or diphosphopyridine nucleotide (DPN), and coenzyme II (65 R = P03H2) also called triphosphopyridine nucleotide (TPN) or nicotinamide adenine dinucleotide phosphate (NADP). These are involved in many oxidation-reduction processes, the quaternized pyridine system acting as a hydrogen acceptor and hydrogen donor. Deficiency of nicotinamide causes pellagra, a disease associated with an inadequately supplemented maize diet. Nicotinic acid (niacin) and its amide are... 

Some enzymes cannot function by themselves. In order to work, they must first be attached to coenzymes. Coenzymes normally are not protein materials. Some of the vitamins are important coenzymes. 

In addition to enzymes, biological oxidations require substances known as coenzymes. Coenzymes are organic molecules that, in concert with an enzyme, act on a substrate to bring about chemical change. Most of the substances that we call vitamins are coenzymes. The coenzyme contains a functional group that is complementary to a functional group of the substrate the enzyme catalyzes the interaction of these mutually complementary functional groups. If ethanol is oxidized, some other substance must be reduced. This other substance is the oxidized form of the coenzyme nicotinamide adenine dinucleotide (NAD). Chemists and biochemists abbreviate the oxidized form of this... 

B vitamins are complex, water-soluble organic chemicals, often containing heterocyclic ring systems (containing one or more atoms other than carbon atoms) they cannot be synthesized by humans and are, therefore, required nutrients. Each of these vitamins is converted by the body into a coenzyme. Coenzymes are cofactors essential to the catalytic activity of enzymes. 

Cofactors that are organic molecules are called coenzymes. Coenzymes are derived from organic compounds commonly known as vitamins. Table 25.1 lists the vitamins and their biochemically active coenzyme forms. 

The refers to the binding of the 2-carbon compound with a special coenzyme. Coenzyme A. The 1-carbon product is carbon dioxide. Pymvate can also be metabolized anaerobically, in which case it receives electrons that were initially removed during glycolysis ... 

Coenzyme Q is capable of accepting either one or two electrons to form either a semiquinone or hydroquinone form. Figure 11-4 shows the quinone, semiquinone, and hydroquinone forms of the coenzyme. Coenzyme Q is not bound to a protein instead it is a mobile electron carrier and can float within the inner membrane, where it can transfer electrons from Complex I and Complex II to Complex 111. 

Some enzymes require the presence of a co ctor. The cofactor may be a metal ion as, for example, the zinc atom of human carbonic anhydrase (see the Chemistry of.. .box, Sertion 24.10 and Fig. 24.12). Others may require the presence of an organic molecule, such as NAD" (Section 14.10), called a coenzyme. Coenzymes become chemically changed in the course of the enzymatic reaction. NAD becomes converted to NADH. In some enzymes the cofactor is permanently bound to the enzyme, in which case it is called a prosthetic group. 

C62H88C0N13O14P 1329.363 Homolysis fragment of coenzyme Coenzyme B12 and Methylcobalamin. 

Cofactors that are organic molecules are called coenzymes. Coenzymes are derived from organic compounds commonly known as vitamins. The first such compound recognized to be essential in the diet was an amine (vitamin Bj), which led scientists to conclude incorrectly that all such compounds were amines. As a result, they were originally called vitamines ( amines required for life ). The e was later dropped from the name. Table 24.1 lists the vitamins and their chemically active coenzyme forms. 

Cofactors that are organic molecules are called coenzymes coenzymes are derived from vitamins, which are substances needed in small amounts for normal body function that the body cannot synthesize. 

All the water-soluble vitamins except vitamin C are precursors of coenzymes. Vitamin K is the only water-insoluble vitamin that is a precursor of a coenzyme. Coenzymes play a variety of chemical roles that the amino acid side chains of enzymes cannot perform. 

In the cell the thioester of dihydrolipoic acid is not stored but is coupled to another sulfur containing coenzyme coenzyme A, CoA-SH, the universal acyl-transfer agent. 

Four decades elapsed before Lipmann (and, independently, Nachmansohn and Berman) discovered that a coenzyme is required for acetylation reactions. From the contributions of many workers we now know that the 2-carbon fragment is an acetylated derivative of this coenzyme, Coenzyme A. 

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