Ribonucleotide 2 ,3 -cyclic phosphate diesterase and

UMP becomes bound to site B which catalyzes the hydrolysis of the phosphomonoester bond. Adenosine and 3 -AMP by binding at site B could interfere with the breakdown of cyclic 2, 3 -UMP. Similarly, binding of bis (p-nitrophenyl) phosphate at site A could interfere with the breakdown of 3 -AMP. Cyclic 2, 3 -UMP and bis(p-nitrophenyl) phosphate compete for site A while adenosine competes with 3 -AMP for site B. Unemoto et al. (7) have examined the mutual inhibition of substrates and substrate analogs for the enzyme from halophilic V. alginolyticus. They also concluded that 3 -ribonucleotides and ribonucleo-side 2, 3 -cyclic phosphates are hydrolyzed at different sites. However, because of the nature of the mutual inhibition between 3 -AMP and bis(p-nitrophenyl) phosphate, they suggested that part of the site for the latter substrate overlaps with the 3 -nucleotidase site. At this time the precise mechanism of action of the enzyme is not settled, but clearly there are two active sites, one a 3 -nucleotidase site and a cyclic phosphate diesterase site. Anraku (18) has described this protein as a double-headed enzyme. 

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See also in sourсe #XX -- [ ]

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