title: Purification and properties of pyridoxal-5'-phosphate-dependent histidine decarboxylases from Klebsiella planticola and Enterobacter aerogenes.
abstract: Histidine decarboxylases from Klebsiella planticola and Enterobacter aerogenes were purified to homogeneity and compared with the histidine decarboxylase from Morganella morganii. All three enzymes required pyridoxal 5'-phosphate as a coenzyme, showed optimal activity at pH 6.5, decarboxylated only histidine among the amino acids derived from protein, and were tetramers or dimers of identical subunits. Amino-terminal sequences of the three enzymes showed up to 81% homology through residue 33, but the enzymes differed sufficiently in amino acid composition and sequence so that no cross-reaction occurred between the K. planticola or E. aerogenes enzymes and antibodies to the decarboxylase from M. morganii. All three enzymes were inhibited by carbonyl reagents; by amino-, carboxyl-, and some methyl-substituted histidines; and by alpha-fluoromethylhistidine. These decarboxylases, all from gram-negative organisms, differed greatly in subunit structure, biogenesis, and other properties from the pyruvoyl-dependent histidine decarboxylases from gram-positive organisms described previously.
mesh_terms: D000595:Amino Acid Sequence; D002262:Carboxy-Lyases / Q000302:isolation & purification*; D003067:Coenzymes / Q000378:metabolism; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D004754:Enterobacter / Q000201:enzymology*; D004755:Enterobacteriaceae / Q000201:enzymology*; D006639:Histidine / Q000378:metabolism; D006640:Histidine Decarboxylase / Q000032:analysis / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D005779:Immunodiffusion; D007709:Klebsiella / Q000201:enzymology*; D008970:Molecular Weight; D011732:Pyridoxal Phosphate / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D013379:Substrate Specificity
chemical_list: D003067:Coenzymes; D006639:Histidine; D011732:Pyridoxal Phosphate; D002262:Carboxy-Lyases; D006640:Histidine Decarboxylase