Ribulose Diphosphate Carboxylase from Freshly Ruptured Spinach Chloroplasts Having an in Vivo Km[CO2]
Open Access
- 1 January 1974
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 53 (1), 39-44
- https://doi.org/10.1104/pp.53.1.39
Abstract
The properties of a form of ribulose diphosphate carboxylase having a high affinity for CO2 have been studied. Its apparent Km(HCO3−) of 0.5 to 0.8 mm (pH 7.8) and calculated Km(CO2) of 11 to 18 μm are comparable to the values exhibited by intact chloroplasts during photosynthesis. This form of the enzyme was released from chloroplasts in hypotonic media and was unstable, rapidly converting to a form having a high Km(HCO3−) of 20 to 25 mm similar to that for the purified enzyme. Incubation of the enzyme with MgCl2 and HCO3− yielded a third form with an intermediate Km(HCO3−) of 2.5 to 3.0 mm.Keywords
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