The critical structural role of a highly conserved histidine residue in group II amino acid decarboxylases

Glutamate decarboxylase is a pyridoxal 5'-phosphate (PLP)-dependent enzyme, belonging to the subset of PLP-dependent decarboxylases classified as group II. Site-directed mutagenesis of Escherichia coli glutamate decarboxylase, combined with analysis of the crystal structure, shows that a histidine residue buried in the protein core is critical for correct folding. This histidine is strictly conserved in the PF00282 PFAM family, which includes the group II decarboxylases. A similar role is proposed for residue Ser269, also highly conserved in this group of enzymes, as it provides one of the interactions stabilising His241. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.