Raines, CA; Harrison, EP; Olcer, H; Lloyd, JC

Sedoheptulose-1,7-bisphosphatase (SBPase; EC 3.1.3.37) catalyses the dephosphorylation of sedoheptulose-1,7-bisphosphate in the regenerative phase of the Calvin cycle, Antisense plants with reduced levels of SBPase have decreased photosynthetic capacity and altered carbohydrate status, leading to modifications in growth and development. The catalytic activity of SBPase is regulated by light via the ferredoxin/thioredoxin system. Recently, the amino acids within the SBPase protein involved in this regulatory mechanism have been identified and a deregulated, permanently active form of the enzyme has been produced using site-directed mutagenesis, This paper explores how transgenic Nicotiana tabacum cv, Samsun plants, containing the deregulated form of the SBPase enzyme, may lead to a better understanding of the in vivo role of light activation of this important Calvin cycle enzyme.