Function of coenzymes

Ebert S, P-G Rieger, H-J Knackmuss (1999) Function of coenzyme P420 in aerobic catabolism of 2,4,6-trinitro-phenol and 2,4-dinitrophenol by Nocardiodes simplex FJ2-1 A. J Bacterial 181 2669-2674. 

Chapter 3 The Physiologic Roles of Enzymes 33 Table 3-3. Physiologic functions of coenzymes and cofactors. 

We present here the mechanisms for four enzymes chymotrypsin, hexoldnase, enolase, and lysozyme. These examples are not intended to cover all possible classes of enzyme chemistry. They are chosen in part because they are among the best understood enzymes, and in part because they clearly illustrate some general principles outlined in this chapter. The discussion concentrates on selected principles, along with some key experiments that have helped to bring these principles into focus. We use the chymotrypsin example to review some of the conventions used to depict enzyme mechanisms. Much mechanistic detail and experimental evidence is necessarily omitted no one book could completely document the rich experimental history of these enzymes. Also absent from these discussions is the special contribution of coenzymes to the catalytic activity of many enzymes. The function of coenzymes is chemically varied, and we describe each as it is encountered in Part II. 

Crane FL (2001) Biochemical functions of coenzyme QIO. Journal of the American College of Nutrition 20, 591-8. 

Airth RL, Rhodes WC, McElroy WD. The function of coenzyme A in luminescence. Biochim Biophys Acta 1958 27 519-32. 

A substantial number of pharmaceutically and clinically related problems require the detection and determination of small amounts of metal ions and other inorganic constituents of biological and xenobiotic substances (1-3). Some obvious examples are the detections of heavy metals and lithium in biological fluids and tissue samples in cases of suspected intoxication and the determination of potassium for purposes of quality control in intravenous solutions to be given to cardiac patients. Trace amounts of nonmetals such as selenium and iodine, which are associated with the functions of coenzymes or hormones, also must be analyzed in order to determine their roles in metabolic pathways. 

See also Function of Coenzymes, Nitrogenase Reductase (vanadium-containing in Azotobacter)... 

In turning our attention to vitamin B12 and its coenzymes, it should be recognized that present diflFerences in opinions and in the interpretations oflFered on the mechanism of coenzyme Bi2-catalyzed processes are largely a consequence of the complexity of these reactions and the difficulty of interpreting the results of enzymological studies in the absence of empirical data derived from model experiments. The situation is best exemplified by first considering an early mechanism postulated for the function of coenzyme B12 in diol dehydratase, not supported by model studies. Ref. 6 contains a detailed discussion. 

This presentation was of necessity brief. I sincerely believe, however, that carefully selected models intelligently applied will bring us closer to essential aspects of nitrogen fixation and the function of coenzyme Bi2 in enzymes, and I also believe that a promising start has been made toward the solution of these problems. 

Sign in atwww.thomsonedu.com/login and explore a Biochemistry Interactive tutorial on the main functions of coenzyme A. 

Each plant cell manufactures its own fatty acids, since there is no lipid transport in plants. The synthesis begins with acetate which is formed from pyruvate, formed from phosphoglycerate in the Calvin cycle in leaf tissue or via degradation of sugars in seeds or fruits. De novo synthesis of fatty acids takes place in the chloroplasts of vegetative tissues or in plastids of other plant tissues. Acetate is first esterified to the -SH function of coenzyme A (CoA) via an enzyme, acetyl CoA synthetase. Coenzyme A is an adenosine derivative attached to a 4 -phosphopantetheine moiety, a chemical subunit idilch is ubiquitous in the metabolism of fatty acids. 

The catalytic function of coenzyme A in citric acid synthesis. J. biol. 

Symposium on Chemistry and Functions of Coenzyme A (1953). Federation Proc. 13, 673. 

The way in which pantothenic acid is incorporated in the molecule of coenzyme A is shown in Fig. P-5. The sulphydryl (-SH) group of the molecule is extremely active, but the other groups are also involved in some of the functions of coenzyme A. 

Novell GD, Lipmann F (1950) The catalytic function of coenzyme Ain citric acid synthesis. J Biol Chem 182 213-228... 

Labeling experiments show that blood cells infected with P. knowlesi and P. falciparum synthesize coenzyme Q (ubiquinone) from p-hydroxybenzoic acid and that coenzyme Qs is apparently the dominant coenz e Q for P. knowlesi. P. lophurae and P. cynomolgi. s Consequently the synthesis of potential reversible inhibitors of the biosynthesis of function of coenzyme Q0 has been undertaken. 

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