COLD STABILITY OF PYRUVATE, ORTHOPHOSPHATE DIKINASE OF FLAVERIA-BROWNII

The nucleotide sequences of the complementary DNA of pyruvate, Pi diki nase (PPDK) from Flaveria bidentis, a C-4 plant which possesses a cold -sensitive form of PPDK, and Flaveria brownii, a 'C-4-like' plant whic h possesses a cold-tolerant form of PPDK, were determined. PPDK was is olated from the leaves of both Flaveria species and purified and the N -terminal amino acid sequences characterised. Together with a maize PP DK cDNA, cDNA inserts which code for the mature form of PPDK of F. bid entis and of F. brownii were expressed in bacteria and the cold sensit ivity of the expressed PPDK studied. The cold sensitivity of the PPDK expressed in bacteria mimics the cold sensitivity of PPDK found in viv o in all three plant species. This study indicates that the cold sensi tivity of plant PPDK is controlled by the primary structure of the enz yme.