Coenzymes, vitamin

Co Cobaltamin S Coenzyme vitamin Bi2 Dietary vitamin supplement... 

Examples of coenzymes vitamin-derived nucleotides for example adenosine phosphates ATP, ADP, AMP nicotinamide derivatives NAD+, NADH, NADP+, NADPH flavin derivatives FAD, FADH2 coenzyme A (abbreviated to CoA, CoASH or CoA-SH). 

Chlorophyll, and photosynthenc reaction center. 917-919 Chromium carbonyl complexes, bond lengths in, 427 Circular dichrotsm ICD). 496-499 Claasen, H. H., 70 Clathrate compounds, 304-306 Claihro-chelates, 530 Clays. 750 Clementi, E., 31, 32 Closo structures, 798-800. 807 Clostridium pasieurianttm, 934 Clusters, 738, 807-819 Coenzyme, 919 Coenzymes, vitamin B,-,... 

Structure of 5 -deoxyadenosylcobalamin coenzyme (vitamin Bj2). The reactive groups are shown in red. 

C is correct. Acetyl CoA is a coenzyme. Vitamins are components of coenzymes. 

Coenzyme Vitamin Additional Chemical group (s) component transferred Distribution... 

Among six-membered aromatic heterocycles the pyridyl core [262] adopts a central role. In nature, pyridine is the constituting structural unit in the coenzyme vitamin... 

Certain vitamins that serve as coenzymes (vitamin C) or as precursors of coenzymes (all B group vitamins and certain carotenoids) are commercially produced in bulk amounts, which are used for human nutrition and animal husbandry, as antioxidants (vitamins C and E) and food colorants (vitamin B2, carotenoids). Only a fraction of technically manufactured vitamins is used for inclusion in drugs. 

Cofactors that are small organic molecules are called coenzymes. Often derived from vitamins, coenzymes can be either tightly or loosely bound to the enzyme. If tightly bound, they are called prosthetic groups. Loosely associated coenzymes are more like cosubstrates because they bind to and are released from the enzyme just as substrates and products are. The use of the same coenzyme by a variety of enzymes and their source in vitamins sets coenzymes apart from normal substrates, however. Enzymes that use the same coenzyme are usually mechanistically similar. In Chapter 9, we will examine the mechanistic importance of cofactors to enzyme activity. A more detailed discussion of coenzyme vitamins can be found in Section 8.6. 

The uptake of essential trace elements, e.g. Na, K, Ni, Co, Mg , POj", MoOj" and, in the case of auxotrophic mutants, of coenzymes, vitamins, and amino acids requires transport systems. In addition to Na transport (see previous sections), active transport systems for Ni, K, PO3, coenzyme M (H-S-CoM), methyl-coenzyme M (CH3-S-C0M), isoleucine and other branched-chain amino acids have been described in methanogens (for recent literature on ion transport in prokaryotes see refs. [251,252]). 

Water-soluble vitamins Fat-soluble vitamins Acting as a coenzyme Not acting as a coenzyme Vitamin-like agents... 

MISCELLANEOUS COMPOUNDS (including biologically useful reagents, low-molecular-weight bioactive substances, antibiotics, coenzymes, vitamins, lipids, phospholipids, nucleosides, nucleotides and polynucleotides)... 

Enzyme Cofactors or Coenzymes Vitamins and Trace Elements... 

Early nutritional studies divided vitamins into two classes water-soluble vitamins and water-insoluble vitamins (Table 25.1). Vitamins A, D, E, and K are water insoluble. Vitamin K is the only water-insoluble vitamin currently known to function as a coenzyme. Vitamin A is required for proper vision, vitamin D regulates calcium and phosphate metabolism, and vitamin E is an antioxidant. Because they do not function as coenzymes, vitamins A, D, and E are not discussed in this chapter. Vitamins A and E are discussed in Sections 9.8 and 26.7, and vitamin D is discussed in Section 29.6. 

Cofactors assist enzymes in catalyzing a variety of reactions that cannot be catalyzed solely by their amino acid side chains. Cofactors can be metal ions or organic molecules. An enzyme with a tightly bound metal ion is called a metalloenzyme. Cofactors that are organic molecules are called coenzymes and these are derived from vitamins. A vitamin is a substance the body cannot synthesize that is needed in small amounts for normal body function. All the water-soluble vitamins except vitamin C function as coenzymes. Vitamin K is the only water-insoluble vitamin currently recognized to function as a coenzyme. 

Fig. 1. 20 (a) Corrin, corrole, and corphin macrocycles. Notice how C-20 is missing and the numbering of the macrocycle reflects this, (b) Coenzyme vitamin B. ... 

Vitamins are any organic dietary substance necessary for life, health, and growth that do not function by supplying energy. They usually function as coenzymes. Vitamins for one species may not be vitamins for another. Only humans, monkeys, and guinea pigs lack the ability to synthesize ascorbic acid (vitamin C), for instance. Indeed, bacteria in the gut synthesize some essential vitamins, which are absorbed in amounts sufficient to meet daily requirements. The administration of antibiotics for a long period of time could thus result in a vitamin deficiency of the bacterial host. 

Values of biomass specific rates are influenced by both genetic and environmental factors. The genes of a particular microorganism and the composition of the growth medium (including the presence of coenzymes, vitamins, hormones, mineral salts, and a variety of other soluble substrates) can affect the numerical values of the various -rates. Other environmental variables that may influence q -rates are temperature, pH, intensity and wavelength of incident radiation, and ionic strength. 

Crow foot-Hodgkin elucidates the structure of the coenzyme vitamin B12 [75a]. 

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