Expression and characterization of a heterodimer of Streptomyces chromofuscus phospholipase D

Immobilization of Phospholipase D on Silica-Coated Magnetic Nanoparticles for the Synthesis of Functional Phosphatidylserine

In this study, silica-coated magnetic nanoparticles (Fe3O4/SiO2) were synthesized and applied in the immobilization of phospholipase D (PLDa2) via physical adsorption and covalent attachment. The immobilized PLDa2 was applied in the synthesis of functional phosphatidylserine (PS) through a transphophatidylation reaction. The synthesis process and characterizations of the carriers were examined by scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The optimum immobilization conditions were evaluated, and the thermal and pH stability of immobilized and free PLDa2 were measured and compared. The tolerance to high temperature of immobilized PLDa2 increased remarkably by 10°C. Furthermore, the catalytic activity of the immobilized PLDa2 remained at 40% after eight recycles, which revealed that silica-coated magnetic nanoparticles have potential application for immobilization and catalytic reactions in a biphasic system.

Crystal structure of the Bacillus subtilis phosphodiesterase PhoD reveals an iron and calcium-containing active site

The PhoD family of extra-cytoplasmic phosphodiesterases are among the most commonly occurring bacterial phosphatases. The exemplars for this family are the PhoD protein of Bacillus subtilis and the phospholipase D of Streptomyces chromofuscus. We present the crystal structure of B. subtilis PhoD. PhoD is most closely related to purple acid phosphatases (PAPs) with both types of enzyme containing a tyrosinate-ligated Fe³⁺ ion. However, the PhoD active site diverges from that found in PAPs and uses two Ca²⁺ ions instead of the single extra Fe²⁺, Mn²⁺, or Zn²⁺ ion present in PAPs. The PhoD crystals contain a phosphate molecule that coordinates all three active site metal ions and that is proposed to represent a product complex. A C-terminal helix lies over the active site and controls access to the catalytic center. The structure of PhoD defines a new phosphatase active site architecture based on Fe³⁺ and Ca²⁺ ions.

Transcription, expression, localization and immunoreactivity of Chlamydophila pneumoniae Phospholipase D protein

Chlamydophila pneumoniae, a recognized aethiological agent of respiratory infection, is also suspected to play a immuno-pathogenetic role in atherosclerosis by contributing to inflammation and plaque instability. Phospholipase D (PLD) is an enzyme involved in lipid metabolism, in protein transport and signal transduction, all events which can direct or indirect impact on virulence and inflammatory response. To better understand the role of PLD in cell biology and infection by C. pneumoniae, we cloned and expressed the pld gene in Escherichia coli and generated the recombinant PLD (rCpPLD). This product was highly immunogenic in mice, and capable to efficiently detect anti-PLD antibodies in humans. As shown by real-time PCR, PLD gene was expressed in a bi-phasic pattern, with transcriptional peaks corresponding to early and late chlamydial development. Fluorescence microscopy showed that CpPLD localized mostly in the center of inclusion bodies between 8 and 48h from infection and at the periphery of inclusions at 72h. Overall, PLD appears consistently expressed during the developmental cycle of C. pneumoniae and is sensed by the host as an antigen target during infection/exposure to this microorganism. rCpPLD may be a useful tool for future studies concerning the role that this enzyme plays in the pathology of, and immune response to, C. pneumoniae.