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159 - 176
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NADP-dependent enzyme activity of Glucose-6-phosphate-dehydrogenase (G6PDH: E.C.1.1.1.49) has been detected in a significant amount (by spectrophotometry) within both cell compartments of Cyanophora paradoxa, within the cytosol and the cyanoplast. The cyanoplast enzyme shows a pH optimum of 7.8 (in crude cyanoplast extracts) and is precipitating between pH 4.5 to 5. It was enriched about 1800 fold by a three step purification procedure (DEAE-Sephadex A25, Cibachron Blue 3GA-Agarose and Mono Q) with 17% yield of the activity of the crude extract (of isolated cyanoplasts) and with 120 U/mg protein as the final specific activity of the purified enzyme. The apparent molecular mass of the monomeric form is 59 kDa (estimated by SDS-PAGE). Native PAGE shows two oligomeric forms for the enzyme activity: a dimeric (ca. 135 kDa +/- 10 kDa) and a tetrameric (ca. 285 kDa +/- 25 kDa). The product seems to be N-terminally blocked.
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