L-threonine = 2-oxobutanoate + NH4(+) Amino-acid biosynthesis; L-isoleucine biosynthesis; 2-oxobutanoate from L-threonine: step 1/1. Homotetramer. Floral buds of untreated plants. After ABA treatment or mechanical wounding is mostly accumulated in leaves, to a lesser extent in stems, but not in roots (PubMed:1392612). Expressed in anthers, carpel leaves, pith cells, sepals and petals. Not expressed in stomium, vascular bundles, epidermal cells or pollen mother cells (PubMed:7550377). By abscisic acid (ABA), jasmonic acid (JA) and wounding. Belongs to the serine/threonine dehydratase family.