Role of endogenous regucalcin in transgenic rats: Suppression of kidney cortex cytosolic protein phosphatase activity and enhancement of heart muscle microsomal Ca2+-ATPase activity

Bacterial pathogens have developed sophisticated mechanisms of evading the immune system to survive in infected host cells. Central to the pathogenesis of Mycobacterium tuberculosis is the arrest of phagosome maturation, partly through interference with PtdIns signalling. The protein phosphatase MptpB is an essential secreted virulence factor in M. tuberculosis. A combination of bioinformatics analysis, enzyme kinetics and substrate-specificity characterization revealed that MptpB exhibits both dual-specificity protein phosphatase activity and, importantly, phosphoinositide phosphatase activity. Mutagenesis of conserved residues in the active site signature indicates a cysteine-based mechanism of dephosphorylation and identifies two new catalytic residues, Asp165, essential in catalysis, and Lys164, apparently involved in substrate specificity. Sequence similarities with mammalian lipid phosphatases and a preference for phosphoinositide substrates suggests a potential novel role of MptpB in PtdIns metabolism in the host and reveals new perspectives for the role of this phosphatase in mycobacteria pathogenicity.

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Inhibitory effect of regucalcin on protein phosphatase activity in the nuclei of rat kidney cortex

Journal of Cellular Biochemistry ◽

10.1002/jcb.1214 ◽

2001 ◽

Vol 83 (1) ◽

pp. 111-120 ◽

Cited By ~ 6

Author(s):

Yoshiko Morooka ◽

Masayoshi Yamaguchi

Keyword(s):

Phosphatase Activity ◽

Protein Phosphatase ◽

Rat Kidney ◽

Inhibitory Effect ◽

Kidney Cortex ◽

Rat Kidney Cortex

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CrATP as a new inhibitor of ecto-ATPases of trypanosomatids

Parasitology ◽

10.1017/s0031182008005118 ◽

2009 ◽

Vol 136 (1) ◽

pp. 35-44 ◽

Cited By ~ 5

Author(s):

O. C. MOREIRA ◽

P. F. RIOS ◽

F. F. ESTEVES ◽

J. R. MEYER-FERNANDES ◽

H. BARRABIN

Keyword(s):

Trypanosoma Cruzi ◽

Atpase Activity ◽

Phosphatase Activity ◽

Substrate Concentration ◽

Active Sites ◽

External Medium ◽

Disulfonic Acid ◽

Trypanosoma Rangeli ◽

Apparent Affinity

SUMMARYTrypanosomatid protozoa include heteroxenic species some of them pathogenic for men, animals and plants. Parasite membrane contains ecto-enzymes whose active sites face the external medium rather than the cytoplasm. Herpetomonas sp. displayed a Mg2+-dependent ecto-ATPase activity, a Mg-independent ecto-ADPase and an ecto-phosphatase activity. Both, the ecto-ADPase and phosphatase activities were insensitive to CrATP (chromium(III) adenosine 5′-triphosphate complex). Ecto-ATPase activity was reversibly inhibited. At 2 mm ATP the apparent Ki was 4·7±1·0 μm but a fraction of about 40–50% was insensitive to CrATP. Remarkably, at low substrate concentration (0·2 mm) more than 90% of the ecto-ATPase was inhibited with Ki=0·33±0·10 μm. These parameter dependences are interpreted as the presence of 2 ecto-ATPases activities, one of them with high ATP apparent affinity and sensitivity to CrATP. DIDS (4,4 diisothiocyanatostilbene 2,2′ disulfonic acid), suramin and ADP were also effective as inhibitors. Only ADP presented no additive inhibition with CrATP. The pattern of partial inhibition by CrATP was also observed for the ecto-ATPase activities of Leishmania amazonensis, Trypanosoma cruzi and Trypanosoma rangeli. CrATP emerges as a new inhibitor of ecto-ATPases and as a tool for a better understanding of properties and role of ecto-ATPases in the biology of parasites.

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