Pyridoxal phosphate (PLP) dependent enzyme, which catalyzes the cleavage of 2-amino-3-oxobutanoate to glycine and acetyl-CoA. Catalyzes the second reaction step on the main metabolic degradation pathway for L-threonine. acetyl-CoA + glycine = (2S)-2-amino-3-oxobutanoate + CoA Amino-acid degradation; L-threonine degradation via oxydo-reductase pathway; glycine from L-threonine: step 2/2. Translocates to the nucleus upon cold and osmotic stress. Belongs to the class-II pyridoxal-phosphate-dependent aminotransferase family.