1968 Volume 14 Issue 2 Pages 111-119
Both ATP deaminase from Microsporum audouini and acid ADP-deaminating enzyme from Aspergillus melleus were found to catalyze the dechlorination of 6-chloropurine ribotide more rapidly than that of 6-chloropurine riboside. Specific AMP deaminase from rabbit muscle was also confirmed to hydrolyze 6-chloropurine ribotide to IMP and chloride ion.
The Km values of ATP deaminase and acid ADP-deaminating enzyme for 6-chloropurine ribotide were 1.2×10-3M and 1.1×10-3M, respectively, while the Vmax of these two deaminases for dechlorinating activity was about 1/4-1/3 of that for deamination of 5′-AMP. The deamination of ATP deaminase and acid ADP-deaminating enzyme were competitively inhibited by 6-chloropurine ribotide, dechlorination of which, in turn, was competitively inhibited by pyrophosphate and it was suggested that both the deamination and the dechlorination occurred at the same active center on deaminase.
The fact that the dechlorinating activity of ATP deaminase for 6-chloropurine ribotide was greater than that for 6-chloropurine riboside and pyrophosphate inhibition of the dechlorination reaction brought about a more evaluation of the schematic model of ATP deaminase previously proposed by the authors.