Journal of Microbiology

Inhibition of purine nucleoside phosphorylase (PNP) in micrococcus luteus phenylglyoxal: Choi , Hye Seon; J. Microbiol. 1996;34(3):270-273.

Abstract: Micrococcus luteus purine nucleoside phosphorylase (PNP) has been purified and characterized. The physical and kinetic properties have been described previously. Chemical modification of the enzyme was attempted to gain insight on the active site. The enzyme was inactivated in a time-dependent manner by the arginine- specific modifying reagent phenylglyoxal. There was a linear relationship between the observed rate of inactivation and the phenylglyoxal concentration. At 30℃ the bimolecular rate constant for the modification was 0.015 min^-1 mM^-1 in 50 mM NaHCO₃buffer, pH 7.5. The plot of logk versus log phenylglyoxal concentration was a strainght line with a slope enzyme. Preincuation with saturated solutions of substrates protected the enzyme from inhibition of phenylglyoxal, indicating that reactions with phenylglyoxal were directed at arginyl residues essential for the catalytic functioning of the enzyme.

Chemical Midification of Purin Nucleoside Phosphorulase in Serratia marcescens: Choi , Hye Seon; J. Microbiol. 1998;36(2):74-79.

Abstract: Serratia marcescens purine nucleoside phosphorylase (PNP) has been purified and characterized. The physical and kinetic properties have been previously described(Choi, H.S. 1998. Biosci. Biotechnol. Biochem. 62, 667-671). Chemical modification of the enzyme was attempted to gain insight on the active site. The enzyme was inactivated in a time dependent manner by phenylglyoxal or diethylpyrocarbonate (DEPC). There was a linear relationship between the observed rate of inactivation and the phenylglyoxal or DEPC concentration. At 30℃ the bimolecular rate constant for the modification was 0.22 mM^-1 min^-1 in 50 mM NaHCO_3 buffer, pH 7.5, for phenylglyoxal and 1.33 mM^-1min^-1 in 50 mM sodium cotrate, pH 6.0, for DEPC. Preincubation with saturated solutions of substrates protected the enzyme from inhibition by kphenylglyoxal and DEPC, indicating that reactions with these reagents were directed at arginyl and histidyl residues, respectively, which are essential for the catalytic function of the enzyme.

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