A pyridoxal-phosphate protein. The enzyme cleaves a carbon-oxygen bond, releasing CO2, ammonia, and an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form pyruvate and a second ammonia molecule. The latter reaction, which can occur spontaneously, can also be catalysed by EC?3.5.99.10, 2-iminobutanoate/2-iminopropanoate deaminase.