Ribulose bisphosphate carboxylase of high specific activity from anther-derived haploid plants of Nicotiana tabacum

Crystalline ribulose bisphosphate carboxylase was purified from several haploid plants of Nicotiana tabacum obtained by anther-culture. Specific activity of the enzyme ranged from 1.09 to 2.15 μmoles 14CO2 fixed mg protein-1 min-1 in growth chamber grown plants and 0.5 to 1.15 μmoles 14CO2 fixed mg protein-1 min-1 in greenhouse grown plants. No degradation of the large subunit was observed on SDS-PAGE electrophoresis of these purified preparations. A low specific activity of 0.25 units was obtained for a preparation of the enzyme from a plant grown under fluctuating growth conditions. This protein gave an additional band for the large subunit on electrophoresis, presumably a degradation product. Individual differences in specific activity under identical growth conditions in these haploids suggest a possible role for the small subunit in regulation of enzyme activity