BRASSICA-NAPUS CDNAS ENCODING FATTY ACYL-COA SYNTHETASE

From a cDNA library of developing siliques of rapeseed (Brassica napus L.) we have isolated five full-length clones encoding polypeptides of the AMP-binding protein family. Two cDNAs encode fatty acyl-CoA synth etase activity (EC 6.2.1.3). The deduced polypeptides share about 52% identical amino acids. After expression in Escherichia coli the predic ted enzymatic activity was confirmed by in vitro assays and product an alysis. The enzymatic activity for one of the clones was characterized in detail by determination of the K-m for oleic acid (10.4 mu m) and the pH optimum (between 7 and 8). For the three additional clones no e nzymatic activities could be demonstrated after expression in E. coli, although two of them exhibit similarity to either eukaryotic or proka ryotic acyl-CoA synthetases. The sequences are compared to a number of related expressed sequence tags from Brassica and Arabidopsis. Potent ial subcellular locations and functions of the deduced polypeptides wi thin plant cells are discussed.