In enzymology, a cytokinin dehydrogenase (EC 1.5.99.12) is an enzyme that catalyzes the chemical reaction

N⁶-dimethylallyladenine + electron acceptor + H₂O ${\displaystyle \rightleftharpoons }$ adenine + 3-methylbut-2-enal + reduced acceptor

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^{[permanent dead link]} deposited to PDB. 16 of these were of enzymes from maize and two from Arabidopsis.