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Journal of Bacteriology, December 2001, p. 7053-7057, Vol. 183, No. 24
Department of Pharmacology, School of
Medicine, Case Western Reserve University, Cleveland, Ohio 44106
Received 10 August 2001/Accepted 21 September 2001
Salmonella enterica serovar Typhimurium requires
Mn2+, but only a few Mn2+-dependent enzymes
have been identified from bacteria. To characterize Mn2+-dependent enzymes from serovar Typhimurium, two
putative PPP-family protein phosphatase genes were cloned from serovar
Typhimurium and named prpA and prpB. Their
DNA-derived amino acid sequences showed 61% identity to the
corresponding Escherichia coli proteins and 41% identity
to each other. Each phosphatase was expressed in E. coli
and purified to near electrophoretic homogeneity. Both PrpA and PrpB
absolutely required a divalent metal for activity. As with other
phosphatases of this class, Mn2+ had the highest affinity
and stimulated the greatest activity. The apparent
Ka of PrpA for Mn2+ of 65 µM was
comparable to that for other bacterial phosphatases, but PrpB had a
much higher affinity for Mn2+ (1.3 µM). The pH optima
were pH 6.5 for PrpA and pH 8 for PrpB, while the optimal temperatures
were 45 to 55°C for PrpA and 30 to 37°C for PrpB. Each phosphatase
could hydrolyze phosphorylated serine, threonine, or tyrosine residues,
but their relative specific activities varied with the specific
substrate tested. These differences suggest that each phosphatase is
used by serovar Typhimurium under different growth or environmental
conditions such as temperature or acidity.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.24.7053-7057.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
The PPP-Family Protein Phosphatases PrpA and PrpB
of Salmonella enterica Serovar Typhimurium Possess Distinct
Biochemical Properties
*
Corresponding author. Mailing address: Department of
Pharmacology, School of Medicine, Case Western Reserve University,
10900 Euclid Ave., Cleveland, OH 44106-4965. Phone: (216) 368-6187. Fax: (216) 368-3395. E-mail: lxs76{at}po.cwru.edu.
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