This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: Krebs ornithine cycle, Krebs-Henseleit cycle
|Superclasses:||Degradation/Utilization/Assimilation → Inorganic Nutrients Metabolism → Nitrogen Compounds Metabolism|
Some taxa known to possess this pathway include : Homo sapiens
Most organisms have to deal with the excretion of nitrogen waste originating from protein and amino acid catabolism. In aquatic organisms the most common form of nitrogen waste is ammonia (ammonotelism), while land-dwelling organisms developed ways to convert the toxic ammonia to either urea (ureotelism) or uric acid (uricotelism). Generally, birds and saurian reptiles excrete uric acid, while the remaining species, including mammals, excrete urea [Brown59, Brown59a]. Remarkably, tadpoles excrete ammonia, and shift to urea production during metamorphosis [Brown59a].
The urea is formed in the livers of mammals in a cyclic pathway which was initially named the Krebs-Henseleit cycle after its discoverers, and later became known simply as the urea cycle. This cycle was partially deduced by Krebs and Henseleit in 1932 [Krebs32] and was clarified in the 1940s as the roles of citrulline and argininosuccinate as intermediates were understood [Jackson86].
Despite the generalization above, the pathway has been documented not only in mammals and amphibians, but in many other organisms as well, including birds [Stockl74], invertebrates [Linton62, Rijavec65], insects [Pant78, Inokuchi69], plants [Reuter61, Kating63], yeast [Chan72], fungi [Prieur71], and even microorganisms [Hiort67, Eckert68].
Superpathways: superpathway of L-citrulline metabolism
Brown59: Brown, G.W., Cohen, P.P. (1959). "Comparative biochemistry of urea synthesis. I. Methods for the quantitative assay of urea cycle enzymes in liver." J Biol Chem 234(7);1769-74. PMID: 13672961
Brown59a: Brown, G.W., Brown, W.R., Cohen, P.P. (1959). "Comparative biochemistry of urea synthesis. II. Levels of urea cycle enzymes in metamorphosing Rana catesbeiana tadpoles." J Biol Chem 234(7);1775-80. PMID: 13672962
Eckert68: Eckert L, Kating H (1968). "[Studies on the metabolism of urea in microorganisms. VII. Dependence of the specific activity of the enzymes of the ornithine cycle and of urease from the duration of culture and the N source]." Arch Mikrobiol 64(2);173-202. PMID: 5709377
Hiort67: Hiort U, Kleczkowski K, Kating H (1967). "[Investigation on the metabolism of urea in microorganisms. VI. Specific activities of the ornithine-cycle enzymes in Micrococcus denitrificans Beij]." Arch Mikrobiol 55(4);311-9. PMID: 5593971
Prieur71: Prieur P (1971). "[Studies on the metabolism of arginine in Ustilago cynodontis. Demonstration of the enzymes of the urea cycle]." C R Acad Sci Hebd Seances Acad Sci D 272(11);1553-5. PMID: 4996649
Bhaumik04: Bhaumik P, Koski MK, Bergmann U, Wierenga RK (2004). "Structure determination and refinement at 2.44 A resolution of argininosuccinate lyase from Escherichia coli." Acta Crystallogr D Biol Crystallogr 60(Pt 11);1964-70. PMID: 15502303
Cama03: Cama E, Colleluori DM, Emig FA, Shin H, Kim SW, Kim NN, Traish AM, Ash DE, Christianson DW (2003). "Human arginase II: crystal structure and physiological role in male and female sexual arousal." Biochemistry 42(28);8445-51. PMID: 12859189
Chen05a: Chen L, Brugger K, Skovgaard M, Redder P, She Q, Torarinsson E, Greve B, Awayez M, Zibat A, Klenk HP, Garrett RA (2005). "The genome of Sulfolobus acidocaldarius, a model organism of the Crenarchaeota." J Bacteriol 187(14);4992-9. PMID: 15995215
Cox01: Cox JD, Cama E, Colleluori DM, Pethe S, Boucher JL, Mansuy D, Ash DE, Christianson DW (2001). "Mechanistic and metabolic inferences from the binding of substrate analogues and products to arginase." Biochemistry 40(9);2689-701. PMID: 11258880
Di05: Di Costanzo L, Sabio G, Mora A, Rodriguez PC, Ochoa AC, Centeno F, Christianson DW (2005). "Crystal structure of human arginase I at 1.29-A resolution and exploration of inhibition in the immune response." Proc Natl Acad Sci U S A 102(37);13058-63. PMID: 16141327
Editors93: Editors: Abraham L. Sonenshein, James A. Hoch, Richard Losick (1993). "Bacillus subtilis and Other Gram-Positive Bacteria: Biochemistry, Physiology, and Molecular Genetics." American Society For Microbiology, Washington, DC 20005.
Gardan97: Gardan R, Rapoport G, Debarbouille M (1997). "Role of the transcriptional activator RocR in the arginine-degradation pathway of Bacillus subtilis." Mol Microbiol 1997;24(4);825-37. PMID: 9194709
Goodyear04: Goodyear CS, Silverman GJ (2004). "Staphylococcal toxin induced preferential and prolonged in vivo deletion of innate-like B lymphocytes." Proc Natl Acad Sci U S A 101(31);11392-7. PMID: 15273292
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