EXPERIMENTAL-EVIDENCE FOR STRUCTURE-ACTIVITY FEATURES IN COMMON BETWEEN MAMMALIAN HISTIDINE-DECARBOXYLASE AND ORNITHINE DECARBOXYLASE

Common protein motifs between histidine decarboxylase (HDC) and ornith ine decarboxylase (ODC) were detected by computational analysis. Mutan ts were generated and expressed in vitro. In both enzymes, terminal PE ST-region-containing fragments are not essential for decarboxylation ( PEST regions are sequence fragments enriched in proline, glutamic acid , serine and threonine residues in a hydrophilic fragment flanked by c ationic amino acids). The substitution of a very well conserved histid ine residue by alanine causes a severalfold increase of the apparent K -m values for the respective substrates.