title: Histidine decarboxylases from bacteria that colonise the human respiratory tract.
abstract: We investigated whether production of histamine by bacteria isolated from sputum of patients with infective lung diseases could be attributed to the presence of histidine decarboxylase (HD). Twenty gram-positive and 20 gram-negative organisms were studied for their ability to decarboxylate 14C-histidine in vitro over the pH range 4.5-7.5. Of the bacteria investigated, lysates from the gram-negative species Haemophilus influenzae, H. parainfluenzae, Moraxella (Branhamella) catarrhalis and Pseudomonas aeruginosa liberated 14CO2 and histamine from 14C-histidine in the presence of the cofactor pyridoxal phosphate. In contrast, results obtained in the absence of cofactor were similar to those of negative (lysate-free) controls suggesting that the HD enzymes of these species resembled those previously described in other gram-negative bacteria. No HD activity was detected over this pH range in lysates from gram-positive species. This finding correlated with earlier observations that these gram-positive organisms did not produce histamine in vitro.
authors.affiliation: Department of Respiratory Medicine, St Bartholomew's Hospital and Medical College, West Smithfield, London.
authors.forename: D R
authors.initials: DR
authors.lastname: Cundell
authors.forename: J L
authors.initials: JL
authors.lastname: Devalia
authors.forename: M
authors.initials: M
authors.lastname: Wilks
authors.forename: S
authors.initials: S
authors.lastname: Tabaqchali
authors.forename: R J
authors.initials: RJ
authors.lastname: Davies
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D002250:Carbon Radioisotopes; D006090:Gram-Negative Bacteria / Q000201:enzymology*; D006094:Gram-Positive Bacteria / Q000201:enzymology*; D006636:Histamine Release; D006640:Histidine Decarboxylase / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D012141:Respiratory Tract Infections / Q000378:metabolism / Q000382:microbiology*
chemical_list: D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; D006640:Histidine Decarboxylase