Addendum to 136] Glutamine-α-keto acid aminotransferase (rat liver)

Abstract

Publisher Summary This chapter describes the assay, purification, and properties of glutamine- α -keto acid aminotransferase. Glutaminase II that catalyzes the deamidation of glutamine in rat liver requires the presence of α- keto acid. The glutaminase II reaction involves the action of two enzymes. The first of these is glutamine transaminase, which gives α -ketoglutaramic acid as a product. The second enzyme is α -keto acid- ω -amidase, which catalyzes the deamidation of α -ketoglutaramic acid to α -ketoglutaric acid. The preparation of glutamine transaminase involves purification of about 700-fold; the enzyme is essentially homogeneous on acrylamide gel electrophoresis and does not exhibit amidase, glutamate–aspartate transaminase, or glutamate–alanine transaminase activities. Enzyme activity may be determined by following the rate of decrease of glutamine or α -keto acid, formation of the new amino acid or α -ketoglutaramate, and formation of α -ketoglutarate or ammonia in preparations that contain α -keto acid- ω -amidase activity. All steps of purification are carried out at 4°. The enzyme can be stored frozen at -20° for at least seven weeks without appreciable loss of activity.