Isolated enzymes iodide

Carbonic anhydrase (CA) exists in three known soluble forms in humans. All three isozymes (CA I, CA II, and CA III) are monomeric, zinc metalloenzymes with a molecular weight of approximately 29,000. The enzymes catalyze the reaction for the reversible hydration of C02. The CA I deficiency is known to cause renal tubular acidosis and nerve deafness. Deficiency of CA II produces osteopetrosis, renal tubular acidosis, and cerebral calcification. More than 40 CA II-defi-cient patients with a wide variety of ethnic origins have been reported. Both syndromes are autosomal recessive disorders. Enzymatic confirmation can be made by quantitating the CA I and CA II levels in red blood cells. Normally, CA I and CAII each contribute about 50% of the total activity, and the CAI activity is completely abolished by the addition of sodium iodide in the assay system (S22). The cDNA and genomic DNA for human CA I and II have been isolated and sequenced (B34, M33, V9). Structural gene mutations, such as missense mutation, nonsense... 

The coenzyme evidently functions in a cyclic process. The cobalt alternates between the +1 and +3 oxidation states as shown in Eq. 16-43. The first indication of such a cyclic process was the report by Weissbach that 14C-labeled methylcobalamin could be isolated following treatment of the enzyme with such methyl donors as AdoMet and methyl iodide... 

High dilution effects were observed in in vitro tests involving isolated organs, cell cultures or macromolecules such as proteins. Mercuric chloride 30c and Mercuric iodide 30c enhanced an enzyme activity in vitro. Unlike high dilutions in aqueous ethanol, efficacy of high dilutions in water deteriorates over time. Mere cor 30 and Nux vom 30 altered water permeation in fish erythrocytes in vitro thereby indicating the influence of high dilution on water channel proteins or aquaporins on plasma membranes. 

Bromoperoxidase activity is expressed as micromoles of mcd brominated per minute per milligram of enzyme (U/mg). The early work on V-BrPO employed the oxidation of iodide by dihydrogen peroxide [1], forming triiodide (Ir), which was followed spectrophotometrically at 353 nm ( = 26,400 M 1cm 1). However, this reaction is less desirable for quantitation of haloperoxidase activity because of competing side reactions, such as the nonenzymatic oxidation of iodide by dihydrogen peroxide and reduction of triiodide by dihydrogen peroxide (discussed later). The specific activity of mcd bromination for V-BrPO isolated from A. nodosum is 170 U/mg (at pH 6.5, 2 mM H202, 0.1 M Br , 50 nM mcd,... 

Before the iodide which is concentrated by the thyroid can react with tyrosine, it must be oxidized to iodine. This oxidation must be enzymic, but all attempts to isolate an oxidizing enzyme from the thyroid have so far failed. Dempsey (1944, 1949), however, has demonstrated, by chemocytological methods, both oxidase and peroxidase activity in the gland, the latter being found in follicular cells. De Robertis and Grasso... 

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