Potassium cofactor

Potassium the prindpal inorganic cation cofactor for some enzymes. 

For each Biocatalytics (Codexis Pasadena) ketoreductase enzyme, 50 pF each of the substrate, cofactor and glucose solutions were added to 350 pF 0.1m potassium phosphate buffer pH 7, 1 mg ketoreductase and 1 Mg glucose dehydrogenase enzymes in one location of a 96-well plate. 

The DDI conventional inhibition screen is moderate throughput and can range from a few compounds per week to a few hundred per week depending on the amount of inhibitor concentrations, inhibition curve replicates and analytical methods used. This screen typically uses 96- or 384-well formats. The reaction components (HLM, 100 mM potassium phosphate buffer, specific probe substrate, NCE, NADPH cofactor or NAD PH-regenerating system) are pre-warmed to 37 °C and are mixed together to initiate the reaction, then incubated at 37 °C for the appropriate length of... 

Pyridoxine (vitamin Bg, 18) (Fig. 13) assists in the balancing of sodium and potassium as well as promoting red blood cell production. A lack of pyridoxine can cause anemia, nerve damage, seizures, skin problems, and sores in the mouth. It is required for the production of the monoamine neurotransmitters serotonin, dopamine, norepinephrine, and epinephrine, as it is the precursor to pyridoxal phosphate, which is the cofactor for the aromatic amino acid decarboxylase enzyme. 

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. 

Fig. 9.12 Effects of /3-phenyl-DL-scrine and L-threonine on absorption (A) and linear dichroism (B) spectra of gel-oriented tryptophanase in 100mM potassium phosphate buffer, pH 7.8. Curve I, unliganded enzyme. Curve 2, same as 1 + 165 mM L-threonine. Curve 3, same as 1 + 15 mM /3-phenyl-DL-serine threo form). (Reproduced with permission from Enzymes Dependent on Pyridoxal Phosphate and Other Carbonyl Compounds as Cofactors, p. 282, Pergamon, N. Y. (1991)).

In a typical procedure to study sulfation reactions (Tabrett 2003) the reaction mixtures consists of a 6.25 mM potassium phosphate buffer (pH 7.4), containing 60 pM adenosine 3 -phosphate 5 -phosphosulfate (PAPS) as a cofactor, 75 pg liver cytosolic protein and 0.125-100 pM substrate (4-nitrophenol in the... 

In inosine monophosphate dehydrogenase, the monovalent metal ion accelerates the hydride transfer step of the reaction with apparently few other effects on the enzyme structure. Probably the monovalent cation is involved in helping position the nicotinamide cofactor. The active site and location of the potassium ion are shown in Figure 2. Mycophenolic acid in this diagram is an inhibitor that is thought to lock inosine monophosphate into the active site, as shown. Note the large distance between the inhibitor (in the active site) and the K+. 

Potassium is a cofactor and activates a large variety of enzymes, including glycerol dehydrogenase, pyruvate kinase, L-threonine dehydrase, and ATPase. Its acute toxicity is primarily due to its action as an electrolyte. Excessive or diminished potassium levels can disrupt membrane excitability and influence muscle cell contractility and neuronal excitability. 

The answer is d. (Murray, pp 238-249. Scriver, pp 2165-2194. Sack, pp 121-144. Wilson, pp 287-324.) Propionic acidemia (232000) results from a block in propionyl CoA carboxylase (PCC), which converts propionic to methylmalonic acid. Excess propionic acid in the blood produces metabolic acidosis with a decreased bicarbonate and increased anion gap (the serum cations sodium plus potassium minus the serum anions chloride plus bicarbonate). The usual values of sodium (-HO meq/L) plus potassium ( 4 meq/T) minus those for chloride (-105 meq/L) plus bicarbonate (—20 meq/L) thus yield a normal anion gap of -20 meq/L. A low bicarbonate of 6 to 8 meq/L yields an elevated gap of 32 to 34 meq/L, a gap of negative charge that is supplied by the hidden anion (propionate in propionic acidemia). Biotin is a cofactor for PCC and its deficiency causes some types of propionic acidemia. Vitamin B deficiency can cause methylmalonic aciduria because vitamin Bn is a cofactor for methylmalonyl coenzyme A mutase. Glycine is secondarily elevated in propionic acidemia, but no defect of glycine catabolism is present. 

The addition of heparin to the isolated rat diaphragm previously loaded with rubidium 86 results in change of the inflow of rubidium . Heparin has a permeabilizing action which appears to be due to mobilization of bound potassium and this can be related to a reduction of calcium in the perfusion solution. Karasek and Mourek.i conclude that heparin depresses oxidative processes through an effect on cell permeability it is possible that it adsorbs certain substances such as potassium chloride or acetylcholine. In extracorporeal dialysis , heparin causes an apparent decrease of 60 per cent in plasma calcium concentration. Heparin also forms a chelate-like compound with calcium ions " . This process is usually unimportant as heparin absorbs a maximum of only 5 per cent of its weight of calcium, but with intradermal, intramuscular or subcutaneous administration, heparin may deplete the capillary walls of calcium and cause them to become fragile. Heparin alsc decreases wound strength 6-14 days after operation in some experiments and may delay the union of fractures in bone repair . Heparin, but not chondroitin sulphate or hyaluronic acid, in tissue culture increases the amount of bone resorption in the presence of suboptimal concentrations of parathyroid extracts, and thus may be a cofactor in bone metabolism. ... 

Copper is recognized as an essential metalloelement like sodium, potassium, magnesium, calcium, iron, zinc, chromium, vanadium and manganese [1]. Like essential amino acids, essential fatty acids and essential cofactors (vitamins), essential metalloelements are required for normal metabolic processes but cannot be synthesized de novo and daily dietary intake and absorption are required. The adult body contains between 1.4 mg (22 pmol) and... 

Potassium appears to perform many of the same functions inside the cell that sodium performs in the plasma and interstitial fluid. Potassium, in various ways 1) regulates the maintenance of the osmotic equilibrium of body fluids 2) acts as an available base to neutralize acids 3) maintains an ionic balance between potassium, sodium, calcium, and magnesium, which in turn affects capillary and cell functions and the excitability of nerves and muscles 4) maintains correct water balance in the body and 5) acts as a cofactor in several enzyme systems, including those used for energy transfer and utilization, protein synthesis, and carbohydrate metabolism (Oberleas et al. 

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