Cytokinin dehydrogenase

The 3 substrates of this enzyme are cytokinin (here represented by N⁶-dimethylallyladenine), electron acceptor, and H₂O, whereas its 3 products are adenine, 3-methylbut-2-enal (or other aldehyde in case of different substrate), and reduced acceptor.

This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH group of donors with other acceptors. The systematic name of this enzyme class is N⁶-dimethylallyladenine:acceptor oxidoreductase. Other names in common use include N⁶-dimethylallyladenine:(acceptor) oxidoreductase, 6-N-dimethylallyladenine:acceptor oxidoreductase, and cytokinin oxidase/dehydrogenase abbreviated as CKX.

Structural studies

As of late 2007, 6 structures have been solved for this class of enzymes, with PDB accession codes 1W1O, 1W1Q, 1W1R, 1W1S, 2EXR, and 2Q4W.

As of March 2016, there have been 18 structures deposited to PDB. 16 of these were of enzymes from maize and two from Arabidopsis.

References

Galuszka P, Frebort I, Sebela M, Sauer P, Jacobsen S, Pec P (2001). "Cytokinin oxidase or dehydrogenase? Mechanism of cytokinin degradation in cereals". Eur. J. Biochem. 268 (2): 450–461. doi:10.1046/j.1432-1033.2001.01910.x. PMID 11168382.

Oxidoreductases: CH-NH (EC 1.5)

1.5.1: NAD or NADP acceptor	Dihydrofolate reductase Saccharopine dehydrogenase Methylenetetrahydrofolate reductase

1.5.3: oxygen acceptor	Dihydrobenzophenanthridine oxidase Sarcosine oxidase Proline oxidase

1.5.5: quinone acceptor	Electron-transferring-flavoprotein dehydrogenase

1.5.99	Sarcosine dehydrogenase Cytokinin dehydrogenase

Enzymes

Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Catalytically perfect enzyme Coenzyme Cofactor Enzyme catalysis Enzyme kinetics Lineweaver–Burk plot Michaelis–Menten kinetics

Regulation	Allosteric regulation Cooperativity Enzyme inhibitor

Classification	EC number Enzyme superfamily Enzyme family List of enzymes

Types	EC1 Oxidoreductases(list) EC2 Transferases(list) EC3 Hydrolases(list) EC4 Lyases(list) EC5 Isomerases(list) EC6 Ligases(list)

Protein: flavoproteins

Acetolactate synthase Acyl CoA dehydrogenase Apoptosis-inducing factor Butyryl CoA dehydrogenase Cryptochrome Cytochrome b5 reductase Cytokinin dehydrogenase Dihydrolipoamide dehydrogenase Flavodoxin Methemoglobin reductase Methylenetetrahydrofolate reductase NADH dehydrogenase NADPH oxidase Nitrate reductase Sarcosine oxidase Thioredoxin reductase

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