Threonine-degrading enzymes in the chicken

Threonine dehydratase, threonine aldolase, and threonine dehydrogenase activities of liver, kidney, skeletal muscle, duodenum, heart, whole brain, and pancreas of the chick (Gallus domesticus) were determined. The highest activities of threonine dehydratase and threonine aldolase were found in liver and muscle and the highest threonine dehydrogenase in the pancreas. Threonine aldolase was more active than threonine dehydratase in all tissues except kidney and intestine, both of which had low activities of these enzymes. Chick liver threonine dehydratase and threonine dehydrogenase, but not threonine aldolase, activities varied significantly during a 24-hr period.