Cofactors, enzymes

Adenosine. Adenosine [58-61-7] (Ado), (29), a purine nucleoside, is an intracellular constituent acting as both an enzyme cofactor... 

Fohc acid is a precursor of several important enzyme cofactors required for the synthesis of nucleic acids (qv) and the metaboHsm of certain amino acids. Fohc acid deficiency results in an inabiUty to produce deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and certain proteins (qv). Megaloblastic anemia is a common symptom of folate deficiency owing to rapid red blood cell turnover and the high metaboHc requirement of hematopoietic tissue. One of the clinical signs of acute folate deficiency includes a red and painhil tongue. Vitamin B 2 folate share a common metaboHc pathway, the methionine synthase reaction. Therefore a differential diagnosis is required to measure foHc acid deficiency because both foHc acid and vitamin B 2 deficiency cause... 

This chapter lists some representative examples of biochemicals and their origins, a brief indication of key techniques used in their purification, and literature references where further details may be found. Simpler low molecular weight compounds, particularly those that may have been prepared by chemical syntheses, e.g. acetic acid, glycine, will be found in Chapter 4. Only a small number of enzymes and proteins are included because of space limitations. The purification of some of the ones that have been included has been described only briefly. The reader is referred to comprehensive texts such as the Methods Enzymol (Academic Press) series which currently runs to more than 344 volumes and The Enzymes (3rd Edn, Academic Press) which runs to 22 volumes for methods of preparation and purification of proteins and enzymes. Leading referenees on proteins will be found in Advances in Protein Chemistry (59 volumes. Academic Press) and on enzymes will be found in Advances in Enzymology (72 volumes, then became Advances in Enzymology and Related Area of Molecular Biology, J Wiley Sons). The Annual Review of Biochemistry (Annual Review Inc. Patio Alto California) also is an excellent source of key references to the up-to-date information on known and new natural compounds, from small molecules, e.g. enzyme cofactors to proteins and nucleic acids. 

Enzyme Cofactors Some Metal Ions and Coenzymes and the Enzymes with Which They Are Associated... 

Therapeutic Function Enzyme Cofactor vitamin source Chemicel Name Sae Structural Formula... 

Mannose, one of the eight essential monosaccharides (Section 25.7), is biosynthesized as its 6-phosphate derivative from fructose 6-phosphate. No enzyme cofactor is required. Propose a mechanism. 

What enzyme cofactor is associated with each of the following kinds of reaction s ... 

The different pro- and anticoagulatory systems are complex regulated cascades involving blood cells (platelets, monocytes, endothelial cells), enzymes, cofactors, phospholipids, and calcium, which interact with each other... 

Barium, effectiveness as cofactor for, see also Enzyme cofactors phospholipase, 204 SNase, 200-204 Bond-breaking processes, 12 potential surfaces for, 13-14, 18-20 in solutions, 22,46-54... 

Chymotrypsin, 170,171, 172, 173 Classical partition functions, 42,44,77 Classical trajectories, 78, 81 Cobalt, as cofactor for carboxypeptidase A, 204-205. See also Enzyme cofactors Condensed-phase reactions, 42-46, 215 Configuration interaction treatment, 14,30 Conformational analysis, 111-117,209 Conjugated gradient methods, 115-116. See also Energy minimization methods Consistent force field approach, 113 Coulomb integrals, 16, 27 Coulomb interactions, in macromolecules, 109, 123-126... 

Enzyme active sites, 136,148, 225. See also Protein active sites in carbonic anhydrase, 197-199 in chymotrypsin, 173 in lysozyme, 153, 157 nonpolar (hypothetical site), 211-214 SNase, 189-190,190 steric forces in, 155-158, 209-211, 225 in subtilisin, 173 viewed as super solvents, 227 Enzyme cofactors calcium ... 

Metal ions, effect of size, 200-205 Metalloenzymes, see also Enzyme cofactors classification of, by cofactor and coupled general base, 205-207, 206 electrostatic interactions in, 205-207 SNase, 189-197... 

See also Enzyme cofactors downhill trajectories for, 196,197 mechanism of catalytic reaction, 190-192 metal substitution, 200-204 potential surfaces for, 192-195,197 rate-limiting step of, 190 reference solution reaction for, 192-195,... 

Strontium, see also Enzyme cofactors effectiveness as cofactor for phospholipase, 204... 

Zinc, see also Enzyme cofactors as cofactor for alcohol dehydrogenase, 205 as cofactor for carbonic anhydrase, 197-200... 

Apohpoproteins carry out several roles (1) they can form part of the stmcture of the hpoprotein, eg, apo B (2) they are enzyme cofactors, eg, C-11 for lipoprotein hpase, A-1 for lecithinicholesterol acyltransferase, or enzyme inhibitors, eg, apo A-11 and apo C-111 for lipoprotein hpase, apo C-1 for cholesteryl ester transfer protein and (3) they act as hgands for interaction with lipopro-... 

The water-soluble vitamins comprise the B complex and vitamin C and function as enzyme cofactors. Fofic acid acts as a carrier of one-carbon units. Deficiency of a single vitamin of the B complex is rare, since poor diets are most often associated with multiple deficiency states. Nevertheless, specific syndromes are characteristic of deficiencies of individual vitamins, eg, beriberi (thiamin) cheilosis, glossitis, seborrhea (riboflavin) pellagra (niacin) peripheral neuritis (pyridoxine) megaloblastic anemia, methyhnalonic aciduria, and pernicious anemia (vitamin Bjj) and megaloblastic anemia (folic acid). Vitamin C deficiency leads to scurvy. 

The water-soluble vitamins of the B complex act as enzyme cofactors. Thiamin is a cofactor in oxidative... 

Lequea et al. used the activity of tyrosine apodecarboxylase to determine the concentration of the enzyme cofactor pyridoxal 5 -phosphate (vitamin B6). The inactive apoenzyme is converted to the active enzyme by pyridoxal 5 -phosphate. By keeping the cofactor the limiting reagent in the reaction by adding excess apoenzyme and substrate, the enzyme activity is a direct measure of cofactor concentration. The enzymatic reaction was followed by detecting tyramine formation by LCEC. The authors used this method to determine vitamin B6 concentrations in plasma samples. 

The fact that N1 is preferentially protonated is in agreement with crystal data obtained for free triazines and enzyme-bound triazines in ternary complex with enzyme and enzyme cofactor (NADPH)45 and also with the difference spectroscopy evidence46 that the N1 of the DHFR-bound MTX is protonated. 

In addition to its broad-spectrum biocidal activity, triclosan (22) displays reversible inhibition of E. coli Fabl with a picomolar K, for binding the enzyme-cofactor complex [4]. Triclosan entry results in the reordering of a loop of amino acids close to the active site, making it a slow, tight-binding inhibitor [41]. 

Leucovorin (folinic acid) - enzyme cofactor for thymidylate synthase rescues from methotrexate toxicity potentiates cytotoxicity of fluoro— pyrimidines -occasional nausea -skin rash -headache -rare allergic reactions... 

The amino acid side chains and enzymes cofactors provide functional groups that are used to make the reaction go faster by providing new pathways and by making existing pathways faster. 

Since long retention times are often applied in the anaerobic phase of the SBR, it can be concluded that reduction of many azo dyes is a relatively a slow process. Reactor studies indicate that, however, by using redox mediators, which are compounds that accelerate electron transfer from a primary electron donor (co-substrate) to a terminal electron acceptor (azo dye), azo dye reduction can be increased [39,40]. By this way, higher decolorization rates can be achieved in SBRs operated with a low hydraulic retention time [41,42]. Flavin enzyme cofactors, such as flavin adenide dinucleotide, flavin adenide mononucleotide, and riboflavin, as well as several quinone compounds, such as anthraquinone-2,6-disulfonate, anthraquinone-2,6-disulfonate, and lawsone, have been found as redox mediators [43—46]. 

Anaerobic bio-reduction of azo dye is a nonspecific and presumably extracellular process and comprises of three different mechanisms by researchers (Fig. 1), including the direct enzymatic reduction, indirect/mediated reduction, and chemical reduction. A direct enzymatic reaction or a mediated/indirect reaction is catalyzed by biologically regenerated enzyme cofactors or other electron carriers. Moreover, azo dye chemical reduction can result from purely chemical reactions with biogenic bulk reductants like sulfide. These azo dye reduction mechanisms have been shown to be greatly accelerated by the addition of many redox-mediating compounds, such as anthraquinone-sulfonate (AQS) and anthraquinone-disulfonate (AQDS) [13-15],... 

Reduced flavins (FADH2, FMNH2, and riboflavin) generated by flavin-dependent reductases have been hypothesized to reduce azo dyes in a nonspecific chemical reaction, and flavin reductases have been revealed to be indeed anaerobic azoreductases. Other reduced enzyme cofactors, for example, NADH, NADH, NADPH, and an NADPH-generating system, have also been reported to reduce azo dyes. Except for enzyme cofactors, different artificial redox mediating compounds, especially such as quinines, are important redox mediators of azo dye anaerobic reduction (Table 1). 

As discussed earlier, Azo biological decolorization are mainly reduced in a direct reduction or mediated/indirect reduction with nonspecial azo reductase or reduced enzyme cofactors (Figs. 1 and 3). According to the direct enzymatic reduction mechanism, nonspecial azo reductase can catalyze the transfer of reducing equivalents originating from the oxidation of original electron donor in the azo dyes. In... 

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