Phosphatase activity characterization on the surface of intact bloodstream forms of Trypanosoma brucei

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• 作者：Cedro Fernandes ; Eloise ; Mauro Granjeiro ; José ; Mikio Taga ; Eulá ; zio ; Meyer-Fernandes ; José ; Roberto ; et. al.
• 关键词：Phosphotyrosine phosphatase ; Bloodstream forms ; Trypanosoma brucei ; EDTA ; ethylenediaminetetraacetic acid ; CDTA ; trans-1 ; 2-diaminocyclohexane-N ; N ; N&prime ; N&prime ; -tetraacetic acid ; pCMB ; p-chloromercuribenzoate ; pNPP ; p-nitrophenyl phosphate ; pNP ; p-nitr
• 刊名：FEMS Microbiology Letters
• 出版年：2003
• 出版时间：March 28, 2003
• 年：2003
• 卷：220
• 期：2
• 页码：197-206
• 全文大小：503 K

文摘

Procyclic forms of Trypanosoma brucei possess a phosphatase activity on their external cell surface. This activity, while it dephosphorylates [³²P]phosphocasein, is inhibited weakly by NaF and tartrate but strongly by vanadate. In this work, we describe the presence of an external phosphatase activity in intact bloodstream forms of T. brucei. With p-nitrophenyl phosphate (pNPP) as substrate, these intact cells produced 3–5 nmol pNP min⁻¹ mg⁻¹, linearly for up to at least 30 min. The activity was not significantly increased by Mg²⁺, Mn²⁺, Ca²⁺ and Co²⁺, but was inhibited by vanadate, NaF, p-chloromercuribenzoate and Zn²⁺ and was insensitive to okadaic acid. Membrane-enriched fractions of parasites contained an acid phosphatase activity, with a pH optimum in the range of 4.5–5.5. This activity hydrolyzed phosphotyrosine (40 nmol phosphate min⁻¹ mg⁻¹) better than phosphothreonine or phosphoserine. Partial purification of this phosphatase yielded a single activity band following gel electrophoresis, a K_m value of 0.29 mM with pNPP and was insensitive to the Fe²⁺/H₂O₂/ascorbate system.