Q43305103
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1. vyd. 121 s. : il., tab. ; 29 cm
- Konspekt
- Biochemie. Molekulární biologie. Biofyzika
- NLK Obory
- biochemie
- NLK Publikační typ
- učebnice vysokých škol
The catabolism of cytokinins is a vital component of hormonal regulation, contributing to the control of active forms of cytokinins and their cellular distribution. The enzyme catalyzing the irreversible cleavage of N(6)-side chains from cytokinins is a flavoprotein classified as cytokinin dehydrogenase (CKX, EC 1.5.99.12). CKXs also show low cytokinin oxidase activity, but molecular oxygen is a comparatively poor electron acceptor. The CKX gene family of Arabidopsis thaliana comprises seven members. Four code for proteins secreted to the apoplast, the remainder are not secreted. Two are targeted to the vacuoles and one is restricted to the cytosol. This study presents the purification and characterization of each of these non-secreted CKX enzymes and substrate specificities are discussed with respect to their compartmentation. Vacuolar enzymes AtCKX1 and AtCKX3 were produced in Pichia pastoris and cytosolic enzyme AtCKX7 was expressed in Escherichia coli. The recombinant proteins were purified by column chromatography. All enzymes preferred synthetic electron acceptors over oxygen, namely potassium ferricyanide and 2,3-dimetoxy-5-methyl-1,4-benzoquinone (Q(0)). In slightly acidic conditions (pH 5.0), N(6)-(2-isopentenyl)adenine 9-glucoside (iP9G) was the best substrate for AtCKX1 and AtCKX7, whereas AtCKX3 preferentially degraded N(6)-(2-isopentenyl)adenine 9-riboside-5'-monophosphate (iPMP). Moreover, vacuolar AtCKX enzymes in certain conditions degraded N(6)-(2-isopentenyl)adenine di- and triphosphates two to five times more effectively than its monophosphate.
- MeSH
- Arabidopsis enzymologie genetika metabolismus MeSH
- cytokininy metabolismus MeSH
- elektroforéza kapilární MeSH
- Escherichia coli enzymologie genetika MeSH
- geneticky modifikované rostliny enzymologie genetika MeSH
- oxidoreduktasy genetika metabolismus MeSH
- Pichia enzymologie genetika MeSH
- rekombinantní proteiny metabolismus MeSH
- spektrometrie hmotnostní - ionizace laserem za účasti matrice MeSH
- tabák enzymologie genetika MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
BACKGROUND: Adenine and adenosine-acting aminohydrolases are important groups of enzymes responsible for the metabolic salvage of purine compounds. Several subclasses of these enzymes have been described and given current knowledge of the full genome sequences of many organisms, it is possible to identify genes encoding these enzymes and group them according to their primary structure. METHODS AND RESULTS: This article is a short overview of the enzymes classified as adenine and adenosine deaminase. It summarises knowledge of their occurrence, genetic basis and their catalytic and structural properties. CONCLUSIONS: These enzymes are constitutive components of purine metabolism and their impairment may cause serious medical disorders. In humans, adenosine deaminase deficiency is linked to severe combined immunodeficiency and as such the enzyme has been approved for the first gene therapy trial. The role of these enzymes in plants is unclear, since the activity was has not been detected in extracts and putative genes have not been yet cloned and analyzed. A literature search and amino acid identity comparison show that Ascomycetes contain only adenine deaminase, but not adenosine deaminase, despite the fact that corresponding genes are annotated in databases as the adenosine cleaving enzymes because they share the same conserved domain.
- MeSH
- adenosindeaminasa chemie genetika MeSH
- aminohydrolasy chemie genetika MeSH
- aminokyseliny analýza MeSH
- Bacteria enzymologie MeSH
- lidé MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
