Bacteria heme degradation

Zhu W, A Wilks, I Stojiljkovic (2000) Degradation of heme in Gram-negative bacteria the product of the hemO gene of Neisseriae is a heme oxygenase. J Bacterial 182 6783-6790. 

Notably, nitrile-degrading enzymes (e.g. nitrilase that converts the CN group to carboxylic acid, and nitrile hydratase that produces an amide function) have been described, and they co-exist with aldoxime-degrading enzymes in bacteria (Reference 111 and references cited therein). Smdies in this area led to the proposal that the aldoxime-nitrile pathway, which is implemented in synthesis of drugs and fine chemicals, occurs as a natural enzymic pathway. It is of interest that the enzyme responsible for bacterial conversion of Af-hydroxy-L-phenylalanine to phenacetylaldoxime, an oxidative decarboxylation reaction, lacks heme or flavin groups which are found in plant or human enzymes that catalyze the same reaction. Its dependency on pyridoxal phosphate raised the possibility that similar systems may also be present in plants . 

Vitamin Bjj (8.50, cobalamin) is an extremely complex molecule consisting of a corrin ring system similar to heme. The central metal atom is cobalt, coordinated with a ribofuranosyl-dimethylbenzimidazole. Vitamin Bjj occurs in liver, but is also produced by many bacteria and is therefore obtained commercially by fermentation. The vitamin is a catalyst for the rearrangement of methylmalonyl-CoA to the succinyl derivative in the degradation of some amino acids and the oxidation of fatty acids with an odd number of carbon atoms. It is also necessary for the methylation of homocysteine to methionine. 

A. When red blood cells lyse, hemoglobin is degraded. Bilirubin is produced from heme at an increased rate. The liver converts bilirubin to the diglucuronide at a rapid rate and excretes it into the bile. In the intestine, bacteria convert bilirubin to stercobilins, which give stool its brown color. 

Brown ME, Walker MC, Nakashige TG, lavarone AT, Chang MC (2011) Discovery and characterization of heme enzymes from unsequenced bacteria application to microbial lignin degradation. J Am Chem Soc 133(45) 18006-18009. doi 10.1021/ja203972q... 

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