• Journal of Life Science
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• v.14 no.4
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• pp.608-613
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• 2004

Pyrimidine nucleotide N-ribosidase (pyrimidine 5'-nucleotide phosphoribo (deoxyribo) hydrolase/pyrimidine 5'-nucleoude nucleosidase, EC 3.2.2.10) directly catalyzes pyrimidine 5'-nucleotide to pyrimidine base and ribose (deoxyribo) 5-phosphate. In order to clarify the best nutritional conditions for the growth and the pyrimidine nucleotide N-ribosidase production of Pseudomonas oleovorans ATCC 8062 the effects of various nutrients such as different carbon and nitrogen sources were studied. For the both the growth and the enzyme production, 2% fumarate, 1.5% peptone, 5% corn steep liquor (CSL) and 1% ammonium chloride were excellent carbon and nitrogen sources, respectively. Optimum pH, temperature, and cultivation time for the enzyme production were 7.0, $28^{\circ}C$, and 48 h, respectively. The pyrimidine nucleotide N-ribosidase of P. oleovorans ATCC 8062 was not induced by UMP and its derivatives, and was constitutive enzyme.

• Journal of Microbiology and Biotechnology
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• v.15 no.3
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• pp.573-578
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• 2005

Pyrimidine nucleotide N-ribosidase (pyrimidine 5'-nucleotide phosphoribo(deoxyribo)hydrolase/pyrimidine 5'-nucleotide nucleosidase, EC 3.2.2.10) catalyzes the breakdown of pyrimidine 5'-nucleotide into pyrimidine base and ribose(deoxyribo)-5-phosphate. However, detailed characteristics of the enzyme have not yet been reported. The enzyme was purified to homogeneity 327.9-fold with an overall yield of $6.1\%$ from Pseudomonas oleovorans ATCC 8062. The enzyme catalyzed cytidine monophosphate (CMP) and uridine monophosphate (UMP), but not adenosine monophosphate (AMP) and guanosine monophosphate (GMP). The enzyme optimally metabolized CMP at pH 6.0 and UMP at around 8.5, and the optimum temperature for the overall enzyme reaction was found to be $37^{\circ}C$. The $K_m$ values of the enzyme for CMP (at pH 6.0) and UMP (at pH 8.5) were 1.6 mM and 1.1 mM, respectively. AMP, deoxyCMP, and deoxyUMP were very effective inhibitors of the reaction. Double-reciprocal plots obtained in the absence and in the presence of AMP revealed that this inhibitory effect was of the mixed competitive type with respect to the breakdown of CMP and of the noncompetitive type with respect to the breakdown of UMP. In the presence of AMP, the enzyme followed sigmoid kinetics with respect to each substrate.