PUB - Publikationen an der Universität Bielefeld

Acetyl-CoA carboxylase (EC 6.4.1.2, ACCase) catalyzes the fonnation of malonyl-CoA from acetyl-CoA and HC03- . In plants this reaction is localized in plastids and represents the first committed step in fatty acid biosynthesis. Additionally ACCase provides malonyl-CoA for several pathways in the cytosol like fatty acid elongation, flavonoid fonnation or malonation of different con1pounds (summarized in 1). Complete coding sequences have been cloned and sequenced from various plant species (for review 2). Using a 260-bp ACCase-specific cDNA fragment as probe eleven clones were isolated from a genomic DNA library of Brassica napus reprcsenting three different ACCase genes. One gene has been completely sequenced (3), two other genes were sequenced at their 5' regions. The three identified genes can be divided into two major classes; class I encompassing two genes with an additional coding exon of approximately 300 bp at the 5' end and class II with one gene carrying an intron of 586 bp in its 5' untranslated region. Analysis of the deduced antlno acid sequence of the additional class 1 coding exon domain revealed some characteristics of transit peptides. This indicates that the two classes of genes 1night encode plaslidic and cyloplastic isoforms of ACCase, respectively.