Catalyzes the NAD(+)-dependent oxidation of L-threonine to 2-amino-3-ketobutyrate. To a lesser extent, also catalyzes the oxidation of D-allo-threonine and L-threonine amide, but not that of D-threonine and L-allothreonine. Cannot utilize NADP(+) instead of NAD(+). L-threonine + NAD(+) = (2S)-2-amino-3-oxobutanoate + H(+) + NADH Binds 2 Zn(2+) ions per subunit. Co(2+) and Cd(2+) can exchange for Zn(2+) (PubMed:2007567). Probably contains one structural ion and one catalytic ion that seems to be less tightly bound at the site (PubMed:9784233). Is totally inhibited by EDTA in vitro. Optimum pH is 10.3. At pH 9.0 and 11.0, the activity is 35% and only 6%, respectively, of the optimal level. Amino-acid degradation; L-threonine degradation via oxydo-reductase pathway; glycine from L-threonine: step 1/2. Homotetramer. Belongs to the zinc-containing alcohol dehydrogenase family.