PURIFICATION OF RUBISCO FROM THE THERMOPHILIC CYANOBACTERIUM SYNECHOCOCCUS SP STRAIN A-1

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), the key enzyme of the Calvin Benson cycle, has been purified from a thermophilic cyanobacterium, Synechococcus sp. strain a-1 and characterized. The enzyme is an L8S8-type hexadecamer with a molecular mass of 530 kDa. The enzyme was stable against heat treatment up to 70-degrees-C, which is the highest value among the RuBisCOs so far purified. The K(m) value for ribulose bisphosphate on the carboxylase activity was substantially higher than those observed for RuBisCOs obtained from mesophilic autotrophs. The N-terminal amino acid sequence for the large subunit of the enzyme was highly similar to those of the other cyanobacteria despite the significant differences in heat stability.