Adenosine Monophosphate Nucleosidase from Azotobacter Vinelandii and Escherichia Coli

This chapter describes the purification procedure for the enzyme adenosine monophosphate nucleosidase (AMP nucleosidase) from Azotobacter vinelandii and Escherichia coli. The enzyme differs from enzymes that are usually classified as nucleotide-degrading enzymes in that it exhibits a high degree of specificity for adenosine monophosphate (AMP) as substrate and is essentially inactive unless Mg Adenosine triphosphate (ATP), the allosteric activator, is present. Allosteric inhibition of activity occurs in the presence of P_i. These controls regulate the enzyme activity that has been postulated to control intracellular AMP levels. The resulting adenine is deaminated by adenine deaminase to form hypoxanthine, which is the end-product of AMP catabolism in Azotobacter. AMP nucleosidase is also present in E. coli and has similar kinetic properties. The end-product of AMP catabolism in E. coli appears to be adenine, because adenine deaminase is missing in this organism.