GA3oksidaz

GA3oksidaz, commonly referred to as gibberellin 3-oxidase (GA3ox), is a plant enzyme that occupies a late step in the biosynthesis of the plant growth hormone gibberellin. It belongs to the family of 2-oxoglutarate-dependent dioxygenases and functions to increase the pool of bioactive gibberellins by converting inactive precursors into active forms.

Biochemically, GA3ox catalyzes the 3β-hydroxylation of specific gibberellin precursors. The canonical reactions are the oxidation of GA20 to GA1 and GA9 to GA4, both requiring Fe2+ as a cofactor, 2-oxoglutarate as a co-substrate, and molecular oxygen. The reactions produce succinate and CO2 as byproducts, delivering the active GA molecules GA1 and GA4 that drive GA signaling pathways.

In plants, GA3ox is encoded by a gene family with multiple members in many species (for example, GA3ox1–GA3ox4 in some model plants). These isozymes often show tissue- and development-specific expression patterns, aligning GA3ox activity with physiological needs for active gibberellins in contexts such as stem elongation, seed germination, and flowering. The enzymes can be regulated at the transcriptional level by developmental cues and environmental signals, and they are part of feedback and feedforward loops controlling overall GA homeostasis.

Biological significance of GA3ox lies in its key role in producing bioactive gibberellins that influence plant height, seed germination, dormancy release, and reproductive development. Alterations in GA3ox activity, whether by genetic variation or environmental factors, can lead to changes in growth rate and form, with potential agricultural implications for crop yield and architecture.