The enzymes that salvage adenine (Ade) and adenosine (Ado) have been studied to a greater extent than other
purine enzymes, in part because the salvage cycle is thought to contribute also to the metabolism of cytokinins
Since CK bases/nucleosides are proposed to be the active form of this growth regulator, metabolism by the salvage cycle enzymes could affect the level of active hormone in a plant cell.
Although progress has been made on characterizing adenine salvage metabolism, it remains unclear as to whether plant
cells utilize these enzymes for CK interconversion in vivo.
Further genetic analysis coupled with more sensitive measurements of the CK constituents in relevant mutants will be necessary to resolve this issue.