Isocitrate lyase of the alga Chlorogonium elongatum: Immunological quantification in relation to growth conditions

Isocitrate lyase (EC 4.1.3.1) from the acetate flagellate Chlorogonium elongatum was studied in relation to growth conditions. In cells growing heterotrophically or photoheterotrophically with acetate (2 g · l(-1)) specific activities of 0.453 and 0.335 μmol glyoxylate · min(-1) · mg(-1) protein, respectively, were found in the cell-free extracts. The malate synthase activity of heterotrophically grown Chlorogonium cells was found to be 0.572 nmol · min(-1) · mg(-1) protein. In the presence of inhibitors acting on transcription and translation there was no increase in isocitrate lyase activity; this would indicate that the enzyme was synthesized de novo in response to changing conditions in the surroundings. Using an enzyme immunoassay it was shown that the activity and amount of enzyme rose concomitantly when the cells were supplied with acetate, irrespective of whether they had been cultivated photoheterotrophically or heterotrophically on acetate.