Magnesium enzyme cofactor

Let me sum up. A lot of magnesium enzymes are involved in energy production processes, and, many times, a phosphate-dominated molecule called ATP (adenosine triphosphate) and other cofactors are needed. Magnesium is also involved with enzymes in the metabolism of fatty acids, proteins, and carbohydrates. Magnesium is involved with heart health in the sense that it plays an important part in the interaction of... 

Transfer of a two-carbon unit from a 2-keto sugar to the carbonyl carbon (Ci) of an aldose by a transketolase, which requires thiamine pyrophosphate and magnesium as cofactors. A covalent enzyme-substrate intermediate is formed similar to the one that occurs during the pyruvate dehydrogenase reaction (Chapter 13). 

HES is produced from 93—96% dextrose hydrolyzate that has been clarified, carbon-treated, ion-exchanged, and evaporated to 40—50% dry basis. Magnesium is added at a level of 0.5—5 mAf as a cofactor to maintain isomerase stabiUty and to prevent enzyme inhibition by trace amounts of residual calcium. The feed may also be deaerated or treated with sodium bisulfite at a level of 1—2-mAf SO2 to prevent oxidation of the enzyme and a resulting loss in activity. 

Magnesium sulphate magnesium is an important cellular cation inorganic cofactor for many enzymatic reactions, induding those involving ATP functions in binding enzymes to substrate. 

Magnesium is the second most abundant intracellular cation. Magnesium serves as an essential cofactor for numerous enzymes and in many biochemical reactions, including reactions involving adenosine triphosphate (ATP).17 Magnesium disorders can be multifactorial and can be related to renal function, disease... 

ATP and magnesium were required for the activation of acetate. Acetylations were inhibited by mercuric chloride suggesting an SH group was involved in the reaction either on the enzyme or, like lipoic acid, as a cofactor. Experiments from Lipmann s laboratory then demonstrated that a relatively heat-stable coenzyme was needed—a coenzyme for acetylation—coenzyme A (1945). The thiol-dependence appeared to be associated with the coenzyme. There was also a strong correlation between active coenzyme preparations and the presence in them of pantothenic acid—a widely distributed molecule which was a growth factor for some microorganisms and which, by 1942-1943, had been shown to be required for the oxidation of pyruvate. 

Type II site-specific deoxyribonuclease [EC 3.1.21.4], also referred to as type II restriction enzyme, catalyzes the endonucleolytic cleavage of DNA to give specific, double-stranded fragments with terminal 5 -phosphates. Magnesium ions are required as cofactors. 

Rubber molecules are synthesized from one APP molecule, which initiates the reaction, and the rubber polymer (cw-l,4-polyisoprene) is then polymerized by sequential condensations of the non-allylic IPP (magnesium cations are a required cofactor) with release of a diphosphate at each condensation. After initiation and elongation, a termination event occurs in which the rubber molecule is released from the enzyme. Despite the similar process, remarkable differences exist between plant species with respect to enzymatic reaction mechanisms and product molecular weight. 

The project encompassed the comparative characterization of pyruvate decarboxylase from Z. mohilis (PDC) and benzoylformate decarboxylase from P. putida (BED) as well as their optimization for bioorganic synthesis. Both enzymes require thiamine diphosphate (ThDP) and magnesium ions as cofactors. Apart from the decarboxylation of 2-ketoacids, which is the main physiological reaction of these 2-ketoacid decarboxylases, both enzymes show a carboligase site reaction leading to chiral 2-hydroxy ketones (Scheme 2.2.3.1). A well-known example is... 

Magnesium is a cofactor in several enzyme systems and is a constituent of bone. The magnesium present in poultry diets is usually adequate. Signs of magnesium deficiency include lethargy, panting, gasping and convulsions followed by death. 

Some elements are essential to the composition or function of the body. Since the body is mostly water, hydrogen and oxygen are obviously essential elements. Carbon (C) is a component of all life molecules, including proteins, lipids, and carbohydrates. Nitrogen (N) is in all proteins. The other essential nonmetals are phosphorus (P), sulfur (S), chlorine (Cl), selenium (Se), fluorine (F), and iodine (I). The latter two are among the essential trace elements that are required in only small quantities, particularly as constituents of enzymes or as cofactors (nonprotein species essential for enzyme function). The metals present in macro amounts in the body are sodium (Na), potassium (K), and calcium (Ca). Essential trace elements are chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), magnesium (Mg), molybdenum (Mo), nickel (Ni), and perhaps more elements that have not yet been established as essential. 

A completely different example of cofactor generation in a microsystem is the local production of magnesium ions to control the position of activation of a DNA restriction enzyme (Katsura et al., 2004). Alternative DNA restriction schemes are important to cut DNA at specific positions, different from the conventional molecular biological methods. Control of restriction was achieved by applying a direct current to a needle electrode of magnesium. Only when and where the magnesium ions from this needle were produced, the restriction enzyme became activated. 

Black CB, Cowan JA. 1997. Inert chromium and cobalt complexes as probes of magnesium-dependent enzymes. Evaluation of the mechanistic role of the essential metal cofactor in Escherichia coli exonuclease III. Eur J Biochem 243 684-689. 

Figure 4.1 Overview of strategy for design of an HPLC method to determine enzymatic activity. The reaction tube contains a mix preparation to measure the activity of an ATP pyrophosphohydrolase, which catalyzes the formation of AMP and PPj from ATP. The mix contains the substrate, ATP the buffer, Tris-HCl and magnesium, a metal cofactor. The addition of a sample from the enzyme fraction initiates the primary reaction and also several secondary reactions. Samples of the incubation mixture are withdrawn at intervals (r( and r2), and the reaction is terminated by injection of the samples onto the HPLC column. A representative analysis of each sample is shown. The amount of each component can be calculated from the area of its peak and is graphed as a function of reaction time.

Pyruvate is initially decarboxylated into ethanal by pyruvate decarboxylase. This enzyme needs magnesium and thiamine pyrophosphate as cofactors (Hohmann 1996). Thereafter, alcohol dehydrogenase reduces ethanal to ethanol, recycling the NADH to NAD+. There are three isoenzymes of alcohol dehydrogenase in Saccharomyces cerevisiae, but isoenzyme I is chiefly responsible for converting ethanal into ethanol (Gancedo 1988). Alcohol dehydrogenase uses zinc as cofactor (Ciriacy 1996). 

The alkaline earths are chemically rather similar, and with the exception of beryllium and, to som6 extent, magnesium which have a pronounced tendency towards covalency, they form essentially ionic compounds. Both calcium and magnesium ions play a key role in various physiological processes by acting as cofactors in many enzymic reactions. In contrast beryllium is characterized by its extreme toxicity. (96)... 

Pyruvate carboxylase is a well-known Mn metalloenzyme. The enzyme is a tetramer and contains one biotin cofactor per subunit and one divalent cation per subunit. The enzyme from calf liver, for example, contains four tightly boimd Mn atoms. The enzyme from chicken liver contains two Mn atoms and two Mg atoms. Raising chickens on an Mn-deficient diet results in the production of an Mn-free enzyme, where magnesium ions replace the usually occurring manganese ions. The Mg-containing enzyme is catalytically active, leaving the requirement of the enzyme for Mn in question (Scrutton et al, 1972). 

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