Purification of glucosamine 6-phosphate deaminase from human brain

Abstract

Glucosamine 6-phosphate deaminase, which degrades glucosamine 6-phosphate reversibly to fructose 6-phosphate and ammonia, has been purified 66-fold from human brain. The enzyme has an optimum pH in the range of 8.5-8.7. N-acetyl-glucosamine 6-phosphate activated the enzyme for both synthesis and degradation of glucosamine 6-phosphate. Pyrophosphate, cysteine and ethylene diamine tetracetic acid inhibited the activity of the enzyme. Certain divalent metal ions also activated the enzyme, Mn²⁺ and Hg²⁺ being the most effective, but Cd²⁺ markedly inhibited it. It was found that fructose 6-phosphate and ammonia are the specific substrates for the formation of glucosamine 6-phosphate. The K_m values in the presence of N-acetyl-glucosamine 6-phosphate and Mn²⁺ were, for glucosamine 6-phosphate, 2.5 . 10^-4 M; for fructose 6-phosphate, 3.5 . 10^-3 M and for (NH₄)₂CO₃, 1.6 . 10^-2 M.