Partial purification and properties of rat liver glutaminase

Abstract

1. The mitochondrial enzyme phosphate-dependent glutaminase was partially purified from rat liver. 2. The enzyme had M(r) 290,000 as judged by chromatography on Sepharyl S-300. 3. After sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of the preparation, glutaminase was tentatively identified with a peptide of M(r) 73,500. 4. The concentration-dependence on glutamine was highly sigmoidal, with half-maximum velocity at 22 mM-glutamine. Half-maximum activity was obtained with 5 mM-phosphate. 5. The enzyme required ammonia as an obligatory activator, in agreement with previous reports on intact and sonicated mitochondria. 6. These findings further differentiate liver glutaminase from the phosphate-dependent glutaminase present in kidney and several other tissues.