Catalyzes the cleavage of 2-amino-3-ketobutyrate to glycine and acetyl-CoA. acetyl-CoA + glycine = (2S)-2-amino-3-oxobutanoate + CoA Binds 1 pyridoxal phosphate per subunit. Amino-acid degradation; L-threonine degradation via oxydo-reductase pathway; glycine from L-threonine: step 2/2. Homodimer. Belongs to the class-II pyridoxal-phosphate-dependent aminotransferase family.