Inhibition of the Nucleotidase Effect of Alkaline Phosphatase by β-Glycerophosphate

Abstract

THE co-existence of more than one enzyme which hydrolyses the same substrate creates considerable difficulties when it is important to distinguish between them. Many attempts have been made to assess the hydrolysis of adenosine 5′ monophosphate (5′ AMP) by non-specific alkaline phosphatase (APase, EC 3.1.3.1) when measuring the activity of 5′ nucleotidase (EC 3.1.3.5). These include the use of 5′ AMP and β-glycerophosphate in independent assays for true nucleotidase and nucleotidase+APase¹; inhibition of APase by EDTA² and by L-histidine³; and inhibition of nucleotidase by Ni⁺⁺ (ref. 4). These techniques measure the phosphorus liberated by enzyme activity, at least two assays each in different sets of conditions being required. To the imprecision resulting from the summation of random errors in each assay is added uncertainty regarding the validity of the assumptions adopted, as the extent to which Ni⁺⁺ partially inhibits APase is in dispute^5,6, and the conditions for EDTA inhibition are difficult to define⁷.