title: An alkaline phosphatase/phosphodiesterase, PhoD, induced by salt stress and secreted out of the cells of Aphanothece halophytica, a halotolerant cyanobacterium.
abstract: Alkaline phosphatases (APases) are important enzymes in organophosphate utilization. Three prokaryotic APase gene families, PhoA, PhoX, and PhoD, are known; however, their functional characterization in cyanobacteria largely remains to be clarified. In this study, we cloned the phoD gene from a halotolerant cyanobacterium, Aphanothece halophytica (phoD(Ap)). The deduced protein, PhoD(Ap), contains Tat consensus motifs and a peptidase cleavage site at the N terminus. The PhoD(Ap) enzyme was activated by Ca(2+) and exhibited APase and phosphodiesterase (APDase) activities. Subcellular localization experiments revealed the secretion and processing of PhoD(Ap) in a transformed cyanobacterium. Expression of the phoD(Ap) gene in A. halophytica cells was upregulated not only by phosphorus (P) starvation but also under salt stress conditions. Our results suggest that A. halophytica cells possess a PhoD that participates in the assimilation of P under salinity stress.
authors.affiliation: Faculty of Science and Technology, Meijo University, Nagoya 468-8502, Japan.
authors.forename: Hakuto
authors.initials: H
authors.lastname: Kageyama
authors.forename: Keshawanand
authors.initials: K
authors.lastname: Tripathi
authors.forename: Ashwani K
authors.initials: AK
authors.lastname: Rai
authors.forename: Suriyan
authors.initials: S
authors.lastname: Cha-Um
authors.forename: Rungaroon
authors.initials: R
authors.lastname: Waditee-Sirisattha
authors.forename: Teruhiro
authors.initials: T
authors.lastname: Takabe
mesh_terms: D000469:Alkaline Phosphatase / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D002118:Calcium; D000458:Cyanobacteria / Q000201:enzymology* / Q000235:genetics; D015870:Gene Expression; D008969:Molecular Sequence Data; D010755:Organophosphates / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054712:Salinity; D012965:Sodium Chloride / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D010755:Organophosphates; D010758:Phosphorus; D012965:Sodium Chloride; D000469:Alkaline Phosphatase; D010727:Phosphoric Diester Hydrolases; D002118:Calcium