Progressive release of carboxylating enzymes during mechanical grinding of sugar cane leaves

The progressive release of protein, chlorophyll, phenol oxidase activity and phenolic compounds during the mechanical disruption of sugar cane leaves has been correlated with the release of carboxylating enzymes. Enzymes of the photosynthetic carbon reduction cycle were released in parallel with chlorophyll, the bulk of which was recovered in grana-containing chloroplasts. PEP carboxylase activity followed the release of total protein. Increased activities of the carboxylating enzymes were obtained in the presence of thioglycollate. There is evidence that PEP carboxylase resides in the cytoplasm rather than in either type of chloroplast. These results are discussed in relation to the possible localisation of carboxylation reactions in the sugar cane leaf.