Cloning, expression, characterisation and three-dimensional structure determination of Caenorhabditis elegans spermidine synthase

The polyamine synthesis enzyme spermidine synthase (SPDS) has been cloned from the model nematode Caenorhabditis elegans. Biochemical characterisation of the recombinantly expressed protein revealed a high degree of similarity to other eukaryotic SPDS with the exception of a low affinity towards the substrate decarboxylated S-adenosylmethionine (K-m = 110 mu M) and a less pronounced feedback inhibition by the second reaction product 5 '-methylthioadenosine (IC50 = 430 mu M). The C elegans protein that carries a nematode-specific insertion of 27 amino acids close to its N-terminus was crystallized, leading to the first X-ray structure of a dimeric eukaryotic SPDS. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.