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Title: Identification and Characterization of an Extracellular Alkaline Phosphatase in the Marine Diatom Phaeodactylum tricornutum
Authors: Hung-Yun Lin;Chi-Yu Shih;Hung-Chun Liu;Jeng Chang;Ying-Lan Chen;Yet-Ran Chen;Han-Tso Lin;Yu-Yung Chang;Chun-Hua Hsu;Han-Jia Lin
Contributors: 國立臺灣海洋大學:生命科學暨生物科技學系
Keywords: Alkaline phosphatase
Metal ion
Date: 2013
Issue Date: 2016-08-31T03:06:08Z
Publisher: Marine Biotechnology
Abstract: Abstract: In phosphorus-deficient conditions, Phaeodactylum tricornutum releases an alkaline phosphatase (PtAPase) to the medium that is readily detectable by activity staining. Nucleic acid and amino acid sequence of this alkaline phosphatase (APase) was identified by performing proteomic analysis and database searches. Sequence alignment suggests that PtAPase belongs to the PhoA family, and it possesses key residues at the Escherichia coli PhoA active site. Quantitative PCR results indicate that the induction of APase mRNA transcription is very sensitive to phosphorus availability and population growth. The molecular mass of native PtAPase (148 kDa) determined by gel filtration chromatography indicates that PtAPase, like most PhoA, is homodimeric. Zn and Mg ions are essential cofactors for most PhoA enzymes; however, PtAPase activity did not require Zn ions. In fact, 5 mM Zn2+, Mo2+, Co2+, Cd2+, or Cu2+ inhibited its enzymatic activity, whereas 5 mM Mn2+, Mg2+, or Ca2+ enhanced its enzymatic activity. The responses of PtAPase to divalent metal ions were different from those of most PhoAs, but were similar to the PhoA in a marine bacterium, Cobetia marina. Phylogenetic analysis shows that homologs of PhoA are also present in other diatom species, and that they clustered in a unique branch away from other PhoA members. PtAPase may represent a novel class of PhoA that helps diatoms to survive in the ocean. Quantification of the PtAPase mRNA may help monitor the physiological condition of diatoms in natural environments and artificial bioreactors.
Relation: 15(4)
URI: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/38385
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