Nature and mode of action of NAD and ATP dephosphorylating enzyme from Aspergillus terreus DSM 826.

Abstract

NAD and ATP were dephosphorylated by Aspergillus terreus extracts optimally at pH 8 and 40 degrees C. The data obtained indicate that one phosphohydrolase was involved in the cleavage of all the phosphate linkages of these two energy-carrying molecules, and also indicate that this enzyme can be classified as a non-specific alkaline phosphatase. This is based on the following criteria: during fractionation of the enzymes of the extracts, using Sephadex G-200 column chromatography, the recorded elution diagram showed only one phosphohydrolase activity peak and this peak was the same with NAD, ATP, inorganic pyrophosphate and phenyl phosphate as substrates; the activity profiles with these four substrates were similar; and these four substrates were hydrolyzed at almost constant relative rates. Moreover, the activities of the pooled fractions with these different substrates responded similarly on changing some experimental conditions, such as addition of fluoride to the reaction mixtures or exposing the enzyme preparation to temperatures above 40 degrees C. Chromatographic detection of the intermediates and the products formed during the progression of NAD and ATP dephosphorylation by the most purified fraction of this enzyme was found to be consistent with the following mode of its action: