Thermophilic PHP Protein Tyrosine Phosphatases (Cap8C and Wzb) from Mesophilic Bacteria

Protein tyrosine phosphatases (PTPs) of the polymerase and histidinol phosphatase (PHP) superfamily with characteristic phosphatase activity dependent on divalent metal ions are found in many Gram-positive bacteria. Although members of this family are co-purified with metal ions, they still require the exogenous supply of metal ions for full activation. However, the specific roles these metal ions play during catalysis are yet to be well understood. Here, we report the metal ion requirement for phosphatase activities of S. aureus Cap8C and L. rhamnosus Wzb. AlphaFold-predicted structures of the two PTPs suggest that they are members of the PHP family. Like other PHP phosphatases, the two enzymes have a catalytic preference for Mn2+, Co2+ and Ni2+ ions. Cap8C and Wzb show an unusual thermophilic property with optimum activities over 75 °C. Consistent with this model, the activity-temperature profiles of the two enzymes are dependent on the divalent metal ion activating the enzyme.

Characterization of low molecular weight protein tyrosine phosphatases of Entamoeba histolytica

Entamoeba histolytica is an intestinal protozoan parasite of humans and is endemic in developing countries. E. histolytica has two low molecular weight protein tyrosine phosphatase (LMW-PTP) genes, EhLMW-PTP1 and EhLMW-PTP2, which are expressed in cultured trophozoites, clinical isolates, and cysts. The amino acid sequences of proteins EhLMW-PTP1 and EhLMW-PTP2 showed only one amino acid difference between them at position A85V, respectively. Both genes are expressed in cultured trophozoites, mainly EhLMW-PTP2, and in trophozoites recovered from amoebic liver abscess, the expression of EhLMW-PTP1 is downregulated. We cloned the two genes and purified the corresponding recombinant (rEhLMW-PTPs) proteins. Antibodies anti-rEhLMW-PTP2 showed that during red blood cells uptake by E. histolytica, the EhLMW-PTPs were found in the phagocytic cups based on analysis of fluorescence signals. On the other hand, rEhLMW-PTPs showed an optimum phosphatase activity at pH 6.0 with p-nitrophenyl phosphate as the substrate. They dephosphorylate phosphotyrosine and 3-O-methylfluorescein phosphate, but not phosphoserine or phosphothreonine, and the enzymatic activity is inhibited by orthovanadate. rEhLMW-PTP1 and rEhLMW-PTP2 exhibited optimum temperatures of activities at 60 °C and 58 °C, respectively, with high thermal stability at 50 °C. Also, the rEhLMW-PTPs showed high specific activities and specific km value with pNPP or OMFP as the substrates at the physiological temperature (37 °C).

Effects of SDS on the activity and conformation of protein tyrosine phosphatase from thermus thermophilus HB27

Deciphering the activity-conformation relationship of PTPase is of great interest to understand how PTPase activity is determined by its conformation. Here we studied the activity and conformational transitions of PTPase from thermus thermophilus HB27 in the presence of sodium dodecyl sulfate (SDS). Activity assays showed the inactivation of PTPase induced by SDS was in a concentration-dependent manner. Fluorescence and circular dichroism spectra suggested SDS induced significant conformational transitions of PTPase, which resulted in the inactivation of PTPase, and the changes of α-helical structure and tertiary structure of PTPase. Structural analysis revealed a number of hydrophobic and charged residues around the active sites of PTPase may be involved in the hydrophobic and ionic bonds interactions of PTPase and SDS, which are suggested to be the major driving force to result in PTPase inactivation and conformational transitions induced by SDS. Our results suggested the hydrophobic and charged residues around the active sites were essential for the activity and conformation of PTPase. Our study promotes a better understanding of the activity and conformation of PTPase.

Expression, purification, and characterization of a novel acid phosphatase that displays protein tyrosine phosphatases activity from Metarhizium anisopliae strain CQMa102

The protein tyrosine phosphatase (PTPase) plays an important role in insect immune system. Our group has purified a type of acid phosphatase that could specifically dephosphorylate trans-Golgi p230 in vitro. In order to study this phosphatase further, we have identified and cloned the phosphatase gene from a locust specific Metarhizium anisopliae Strain CQMa102. The CQMa102 phosphatase was expressed in Pichia pastoris to verify its protease activity. The molecular weight (MW) and the isoelectric point (pI) of the phosphatase were about 85 kDa and 6.15, respectively. Substrate specificity evaluation showed that the purified enzyme exhibited high activity on O-phospho-L-tyrosine. At its optimal pH of 6.5 and optimum temperature of 70 °C, the protein showed the highest activity respectively. It can be activated by Ca2+, Mg2+, Mn2+, Ba2+, Co2+ and phosphate analogs, but inhibited by Zn2+, Cu2+, fluoride, dithiothreitol, β-mercaptoethanol and N-ethylmaleimide.

Kinetic characterization of a novel acid ectophosphatase from Enterobacter asburiae

Expression of acid ectophosphatase by Enterobacter asburiae, isolated from Cattleya walkeriana (Orchidaceae) roots and identified by the 16S rRNA gene sequencing analysis, was strictly regulated by phosphorus ions, with its optimal activity being observed at an inorganic phosphate concentration of 7 mM. At the optimum pH 3.5, intact cells released p-nitrophenol at a rate of 350.76 ± 13.53 nmol of p-nitrophenolate (pNP)/min/10(8) cells. The membrane-bound enzyme was obtained by centrifugation at 100,000 × g for 1 h at 4 °C. p-Nitrophenylphosphate (pNPP) hydrolysis by the enzyme follows "Michaelis-Menten" kinetics with V = 61.2 U/mg and K0.5 = 60 μM, while ATP hydrolysis showed V = 19.7 U/mg, K0.5 = 110 μM, and nH = 1.6 and pyrophosphate hydrolysis showed V = 29.7 U/mg, K0.5 = 84 μM, and nH = 2.3. Arsenate and phosphate were competitive inhibitors with K i = 0.6 mM and K i = 1.8 mM, respectively. p-Nitrophenyl phosphatase (pNPPase) activity was inhibited by vanadate, while p-hydroxymercuribenzoate, EDTA, calcium, copper, and cobalt had no inhibitory effects. Magnesium ions were stimulatory (K0.5 = 2.2 mM and nH = 0.5). Production of an acid ectophosphatase can be a mechanism for the solubilization of mineral phosphates by microorganisms such as Enterobacter asburiae that are versatile in the solubilization of insoluble minerals, which, in turn, increases the availability of nutrients for plants, particularly in soils that are poor in phosphorus.

Inactivation and unfolding of protein tyrosine phosphatase from Thermus thermophilus HB27 during urea and guanidine hydrochloride denaturation

The effects of urea and guanidine hydrochloride (GdnHCl) on the activity, conformation and unfolding process of protein tyrosine phosphatase (PTPase), a thermostable low molecular weight protein from Thermus thermophilus HB27, have been studied. Enzymatic activity assays showed both urea and GdnHCl resulted in the inactivation of PTPase in a concentration and time-dependent manner. Inactivation kinetics analysis suggested that the inactivation of PTPase induced by urea and GdnHCl were both monophasic and reversible processes, and the effects of urea and GdnHCl on PTPase were similar to that of mixed-type reversible inhibitors. Far-ultraviolet (UV) circular dichroism (CD), Tryptophan and 1-anilinonaphthalene -8-sulfonic acid (ANS) fluorescence spectral analyses indicated the existence of a partially active and an inactive molten globule-like intermediate during the unfolding processes induced by urea and GdnHCl, respectively. Based on the sequence alignment and the homolog Tt1001 protein structure, we discussed the possible conformational transitions of PTPase induced by urea and GdnHCl and compared the conformations of these unfolding intermediates with the transient states in bovine PTPase and its complex structures in detail. Our results may be able to provide some valuable clues to reveal the relationship between the structure and enzymatic activity, and the unfolding pathway and mechanism of PTPase.