d-Ribulose-1,5-biphosphate carboxylase fromThiobacillus neapolitanus |
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Authors: | R M Snead J M Shively |
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Institution: | (1) Department of Biochemistry, Clemson University, 29631 Clemson, South Carolina, USA |
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Abstract: | d-Ribulose-1,5-bisphosphate carboxylase fromThiobacillus neapolitanus was isolated by differential centrifugation, sucrose density gradient centrifugation, and DEAE-Sephadex column chromatography.
The specific activity of the purified enzyme was 2.8 μmol CO2 fixed/min/mg protein. The enzyme's homogeneity was indicated by a single migrating band during polyacrylamide disc gel electrophoresis
and as a single symmetrical schlieren peak that sedimented at a constant rate during ultracentrifugation. TheS
20,w was 18.2; the molecular weight, 500,000±20.000. Sodium dodecyl sulfate polyacrylamide disc gel electrophoresis resolved two
polypeptide chains of 55,000 and 11,000 daltons. The pH optimum 0f 7.75 with 9 mM MgCl2 shifted to 7.45 with 59 mM MgCl2. Enzyme dialyzed free of Mg++ was inactive and no other divalent cation substituted for Mg++. TheK
m
(Mg++),K
m
(CO2), andK
m
(RuBP) were 0.59 mM, 0.85 mM, and 0.092 mM, respectively. The inhibition by 6-phosphogluconate was competitive and no stimulation
of activity could be demonstrated. |
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Keywords: | |
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