Purification,primary structure,and properties of <Emphasis Type="Italic">Euphorbia characias</Emphasis> latex purple acid phosphatase |
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Authors: | F Pintus D Spano S Corongiu G Floris R Medda |
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Institution: | Department of Applied Sciences in Biosystems, University of Cagliari, Cagliari, Italy. |
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Abstract: | A purple acid phosphatase was purified to homogeneity from Euphorbia characias latex. The native protein has a molecular mass of 130 ± 10 kDa and is formed by two apparently identical subunits, each containing
one Fe(III) and one Zn(II) ion. The two subunits are connected by a disulfide bridge. The enzyme has an absorbance maximum
at 540 nm, conferring a characteristic purple color due to a charge-transfer transition caused by a tyrosine residue (Tyr172)
coordinated to the ferric ion. The cDNA nucleotide sequence contains an open reading frame of 1392 bp, and the deduced sequence
of 463 amino acids shares a very high degree of identity (92–99%) to other purple acid phosphatases isolated from several
higher plants. The enzyme hydrolyzes well p-nitrophenyl phosphate, a typical artificial substrate, and a broad range of natural phosphorylated substrates, such as ATP,
ADP, glucose-6-phosphate, and phosphoenolpyruvate. The enzyme displays a pH optimum of 5.75 and is inhibited by molybdate,
vanadate, and Zn2+, which are typical acid phosphatase inhibitors. |
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