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In this study it is shown that the higher molecular weight previously reported for tiger shark carbonic anhydrase (carbonate hydro-lyase, EC 4.2.1.1) compared to other carbonic anhydrases is decreased to a normal value around 30 000 after disulfide reduction of the enzyme. This difference in molecular weight is at least partly due to the existence of disulfide-linked glutathione and cysteine residues. Approx. 3 mol glutathione and a similar amount of cysteine are shown to be bound per mol enzyme. The presence of these factors also has effects on the enzyme activity. 相似文献
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A N Mats E V Cheprasova S I Elkina E V Koriakin 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1987,(5):67-71
Nonspecific adhesiveness of lymphocytes to polyacrylonitrile fiber and the antigen-specific adhesiveness of T-lymphocytes to Shigella flexneri pellicular immunosorbent have been studied in dysentery patients. Short courses of treatment with indomethacin, but not with thymalin (the preparation of thymic hormones), used for immunomodulation, have accelerated the normalization of nonspecific lymphocyte adhesiveness during regression of the disease, while indomethacin, in contrast to thymalin, inhibits antigen-specific T-lymphocyte adhesiveness which increases with the development of immune response. 相似文献
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M Huber M Lindgren P Hammarstr?m L G M?rtensson U Carlsson G R Eaton S S Eaton 《Biophysical chemistry》2001,94(3):245-256
Phase memory relaxation times (T(M) or T(2)) of spin labels in human carbonic anhydrase II (HCA II) are reported. Spin labels (N-(1-oxyl-2,2,5,5-tetramethyl-3-pyrrolidinyl)iodoacetamide, IPSL) were introduced at cysteines, by site-directed mutagenesis at seven different positions in the protein. By two pulse electron paramagnetic resonance (EPR), electron spin echo decays at 45 K are measured and fitted by stretched exponentials, resulting in relaxation parameters T(M) and x. T(M) values of seven positions are between 1.6 micros for the most buried residue (L79C) and 4.7 micros for a residue at the protein surface (W245C). In deuteriated buffer, longer T(M) are found for all but the most buried residues (L79C and W97C), and electron spin echo envelop modulation (ESEEM) of deuterium nuclei is observed. Different deuterium ESEEM patterns for W95C and W16C (surface residue) indicate differences in the local water concentration, or accessibility, of the spin label by deuterium. We propose T(M) as a parameter to determine the spin label location in proteins. Furthermore, these systems are interesting for studying the pertaining relaxation mechanism. 相似文献
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