The thrH Gene Product of Pseudomonas aeruginosa Is a Dual Activity Enzyme with a Novel Phosphoserine:Homoserine Phosphotransferase Activity

S. Kumar Singh, Kun Yang, Subramanian Karthikeyan, Tu Huynh, Xuejun Zhang, Margaret A. Phillips, Hong Zhang

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

The thrH gene product of Pseudomonas aeruginosa has been shown to complement both homoserine kinase (thrB gene product) and phosphoserine phosphatase (serB gene product) activities in vivo. Sequence comparison has revealed that ThrH is related to phosphoserine phosphatases (PSP, EC 3.1.3.3) and belongs to the L-2-haloacid dehalogenase-like protein superfamily. We have solved the crystal structures of ThrH in the apo-form and in complex with a bound product phosphate. The structure confirms an overall fold similar to that of PSP. Most of the catalytic residues of PSP are also conserved in ThrH, suggesting that similar catalytic mechanisms are used by both enzymes. Spectrophotometry-based in vitro assays show that ThrH is indeed a phosphoserine phosphatase with a Km of 0.207 mM and kcat of 13.4 min-1, comparable with those of other PSPs. More interestingly, using high pressure liquid chromatography-based assays, we have demonstrated that ThrH is able to further transfer the phosphoryl group to homoserine using phosphoserine as the phosphoryl group donor, indicating that ThrH has a novel phosphoserine:homoserine phosphotransferase activity.

Original languageEnglish (US)
Pages (from-to)13166-13173
Number of pages8
JournalJournal of Biological Chemistry
Volume279
Issue number13
DOIs
StatePublished - Mar 26 2004

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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