Ornithine decarboxylase
| Ornithine decarboxylase | ||
|---|---|---|
|
||
| according to PDB 1D7K | ||
| Properties of human protein | ||
| Mass / length primary structure | 461 amino acids , 51,148 Da | |
| Secondary to quaternary structure | Homodimer | |
| Cofactor | Pyridoxal phosphate | |
| Identifier | ||
| Gene name | ODC1 | |
| External IDs | ||
| Enzyme classification | ||
| EC, category | 4.1.1.17 | |
| Response type | Decarboxylation | |
| Substrate | L -Ornithine | |
| Products | Putrescine + CO 2 | |
Ornithine decarboxylase is a protein that catalyzes the decarboxylation of ornithine to putrescine .
properties
Ornithine decarboxylase catalyzes the reaction of L- ornithine to putrescine and CO 2 in animal cells :
Putrescine is the precursor molecule for the polyamines spermidine and spermine , and together with these it is involved in cell proliferation . The activity of the ODC is inhibited by the ornithine decarboxylase antizyme at the end of the S-phase and the ODC is degraded. The expression of the antizyme is induced by the resulting polyamines through negative feedback. The degradation of the ODC is a prominent example of the ubiquitin-independent proteolysis of enzymes.
Ornithine decarboxylase has a short half-life for a protein , in animal cells between 10 minutes and a few hours, depending on the source.
The ODC also catalyzes the synthesis of putrescine in plant roots, which then serves as an intermediate for the synthesis of various alkaloids .
Detection of the bacterial enzyme
Numerous types of bacteria also have ornithine decarboxylase. The detection of the enzyme in representatives of the gram-negative enterobacteria is used for differentiation and is part of a colored series to determine the genus or species . The test procedure was introduced in 1955 and has been part of miniaturized test systems since the 1970s (e.g. in the API 20 E system).
For the detection of the bacterial enzyme - often abbreviated as ODC - the standardized, ornithine- containing nutrient medium is inoculated with bacterial material and incubated under anoxic conditions . In order to prevent oxygen from entering the test tube, the inoculated approach is covered with either paraffin oil or mineral oil . The formation of the diamine putrescine increases the pH value in the test medium; the evaluation is based on the color change of the pH indicator integrated in the nutrient medium . For optimal enzyme activity a pH value below 5.5 is required (acidic range), while nutrient media usually have a neutral pH value.
Various test media
There are differences in the composition of the differentiation medium and the pH indicator used:
In the nutrient medium developed first according to Møller , D - glucose is used in addition to ornithine , as well as bromocresol purple as a pH indicator, the pH value is adjusted to 6.0. The bacteria first utilize the small amount of glucose in a fermentation process , whereby acids are formed (compare mixed acid fermentation ), which lowers the pH value below 5.5. The reaction of the ODC that then sets in alkalizes the test medium and bromocresol purple indicates this by changing the color from yellow to purple . A comparison tube that does not contain ornithine should always be carried so that the initial acid formation can be checked. A disadvantage is that the batch has to be incubated for up to four days before the evaluation can take place. A modification of this differentiation medium is the MIO agar , with which the formation of indole by the bacteria and their motility can also be checked.
A faster variant is a method in which bromocresol purple is also used, but the test medium does not contain any glucose. In addition to ornithine, peptones and yeast extract are used, and the pH is adjusted to 5.5. The liquid nutrient medium is inoculated with plenty of bacterial material and incubated for four hours, after which the ornithine decarboxylase reaction is assessed. A similar, also fast '(Engl. Rapid ) method is also available for the detection of lysine decarboxylase .
Alternatively, phenol red is used as a pH indicator, for example in ODC tests in the API 20 E system. It also does not contain any glucose and the original pH value is set to 6.2. An incubation period of 18 to 24 hours should be observed before the ODC reaction is assessed. The alkalization is indicated by a color change from phenol red from yellow to red; an orange color (pH value just above 7.0) is also to be assessed as positive. If this is observed, an agreement of 99% with the Møller method results.
Examples of ODC-positive and ODC-negative bacteria
The detection of the bacterial ornithine decarboxylase is important for the differentiation of the enterobacteria. Representatives of the genera Buttiauxella , Edwardsiella , Escherichia , Hafnia , Morganella , Shigella and the species Cronobacter sakazakii have this enzyme. In contrast , representatives of the genera Moellerella , Providencia and Rhanella are ODC-negative.
Within the genera Cedecea , Citrobacter , Enterobacter , Klebsiella , Proteus , Salmonella , Serratia and Yersinia there are ODC-positive and -negative representatives, which can be distinguished by the detection of the ornithine decarboxylase reaction. For example, the medically relevant species Enterobacter cloacae , Klebsiella aerogenes (both ODC-positive) and Klebsiella pneumoniae (ODC-negative) can be distinguished. Or the differentiation of Yersinia pestis and Yersinia pseudotuberculosis (both ODC-negative) to other ODC-positive Yersinia species or the differentiation of Proteus mirabilis (ODC-positive) and Proteus vulgaris (ODC-negative, less pathogenic) is possible.
Clinical significance
Ornithine decarboxylase is inhibited by several drugs, including acitretin and tazarotene , two drugs used to treat severe forms of psoriasis , and eflornithine , which is used to treat hirsutism topically in women. In all cases, the inhibition reduces cell growth.
Web links
Individual evidence
- ↑ Peter C. Heinrich, Georg Löffler, Petro E. Petrides (Eds.): Löffler-Petrides Biochemistry and Pathobiochemistry . 8th edition. Springer Medicine, Heidelberg 2007, ISBN 978-3-540-32680-9 , p. 322 .
- ↑ Philipp Christen, Rolf Jaussi, Roger Benoit: Biochemistry and Molecular Biology . Springer, Berlin, Heidelberg 2016, ISBN 978-3-662-46429-8 , pp. 159 , doi : 10.1007 / 978-3-662-46430-4 .
- ↑ Peter C. Heinrich, Georg Löffler, Petro E. Petrides (Eds.): Löffler-Petrides Biochemistry and Pathobiochemistry . 8th edition. Springer Medicine, Heidelberg 2007, ISBN 978-3-540-32680-9 , p. 462 .
- ↑ Rudolf Hänsel, Ernst Steinegger (Ed.): Pharmakognosie - Phytopharmazie . 9., revised. and updated edition. Springer, Heidelberg 2010, ISBN 978-3-642-00962-4 , chapter alkaloids .
- ↑ a b c d e Gunnar D. Fay, Arthur L. Barry: Rapid ornithine decarboxylase test for the identification of enterobacteriaceae . In: Applied Microbiology . tape 23 , no. 4 , April 1972, p. 710-713 , PMID 4553140 , PMC 380423 (free full text).
- ^ Vagn Møller: Simplified tests for some amino acid decarboxylases and for the arginine dihydrolase system . In: Acta pathologica et microbiologica Scandinavica . tape 36 , no. 2 , 1955, pp. 158-172 , doi : 10.1111 / j.1699-0463.1955.tb04583.x , PMID 14375937 .
- ↑ a b c PB Smith, KM Tomfohrde, DL Rhoden, A. Balows: API system: a multitube micromethod for identification of Enterobacteriaceae . In: Applied Microbiology . tape 24 , no. 3 , September 1972, p. 449-452 , PMID 4562482 , PMC 376540 (free full text).
- ↑ a b c Roland Süßmuth, Jürgen Eberspächer, Rainer Haag, Wolfgang Springer: Biochemical-microbiological internship . 1st edition. Thieme Verlag, Stuttgart / New York 1987, ISBN 3-13-685901-4 , p. 78-85 .
- ^ A b c Elmer W. Koneman: Koneman's Color Atlas and Textbook of Diagnostic Microbiology . Lippincott Williams & Wilkins, 2006, ISBN 0-7817-3014-7 , pp. 225–226 ( limited preview in Google Book search).
- ↑ a b JJ Farmer III, BR Davis u. a .: Biochemical identification of new species and biogroups of Enterobacteriaceae isolated from clinical specimens . In: Journal of Clinical Microbiology . tape 21 , no. 1 , January 1985, p. 46-76 , PMID 3881471 , PMC 271578 (free full text).
- ↑ Hasso Scholz, Gustav Kuschinsky, Rainer Böger (ed.): Pocket book of drug treatment: applied pharmacology . 13., revised. and updated edition. Springer, Berlin, Heidelberg, New York 2005, ISBN 3-540-20821-6 , pp. 399; 556; 841 .