ATP citrate lyase in the glaucocystophyte alga Cyanophora paradoxa is a cytosolic enzyme: characterisation of the gene for the large subunit at the cDNA and genomic levels

The single-copy gene for the large subunit of ATP citrate lyase (ACL) from the alga Cyanophora paradoxa was characterized at the cDNA and genome level s. The gene product showed high sequence similarity to its mammalian counte rparts, but is smaller in size, as is also found for the fungal subunit Acl l and, most probably, for the corresponding subunit from Arabidopsis thalia na. The C. paradoxa gene is interrupted by at least 12 introns of 53-65 by with conserved border and branchpoint sequences, and the product lacks a st roma-targeting peptide. Enzyme activity was found in the cytosol of C. para doxa but not in the plastid (cyanelle) fraction. This is in contrast to the subcellular distribution of ATP citrate lyases in higher plants, where bot h chloroplast and cytosolic enzymes have been reported.