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Transphosphatidylation by Phospholipase D
Transphosphatidylase activity was recognized in several plant tissues as well as in extracts. It was attributed to phospholipase D. This enzyme was purified 110-fold from Savoy cabbage. The ratio of its hydrolase to its transphosphatidylase activity remained constant throughout the purification. Additional evidence supports the conclusion that both reactions are catalyzed by the same enzyme. Phosphatidylations of ethanol, ethanolamine, and glycerol were readily achieved by incubating phosphatidylcholine and the enzyme in the presence of one of these acceptors. Concentrations of the acceptors required for equality between rates of hydrolysis and transphosphatidylation were 0.7, 0.3, and 1.1%, respectively, for ethanol, ethanolamine, and glycerol. The glycerol configuration in the phosphatidylglycerol thus produced was DL-; phosphatidylation in this case was not stereospecific. [1]
REGULATION OF EUKARYOTIC PHOSPHATIDYLINOSITOL-SPECIFIC PHOSPHOLIPASE C AND PHOSPHOLIPASE D
This review focuses on two phospholipase activities involved in eukaryotic signal transduction. The action of the phosphatidylinositol-specific phospholipase C enzymes produces two well-characterized second messengers, inositol 1,4,5-trisphosphate and diacylglycerol. This discussion emphasizes recent advances in elucidation of the mechanisms of regulation and catalysis of the various isoforms of these enzymes. These are especially related to structural information now available for a phospholipase C δ isozyme. [2]
Regulation of Phosphoinositide-Specific Phospholipase C
Eleven distinct isoforms of phosphoinositide-specific phospholipase C (PLC), which are grouped into four subfamilies (β, γ, δ, and ∍), have been identified in mammals. These isozymes catalyze the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] to inositol 1,4,5-trisphosphate and diacylglycerol in response to the activation of more than 100 different cell surface receptors. All PLC isoforms contain X and Y domains, which form the catalytic core, as well as various combinations of regulatory domains that are common to many other signaling proteins. These regulatory domains serve to target PLC isozymes to the vicinity of their substrate or activators through protein-protein or protein-lipid interactions. These domains (with their binding partners in parentheses or brackets) include the pleckstrin homology (PH) domain [PtdIns(3)P, βγ subunits of G proteins] and the COOH-terminal region including the C2 domain (GTP-bound α subunit of Gq) of PLC-β; the PH domain [PtdIns(3,4,5)P3] and Src homology 2 domain [tyrosine-phosphorylated proteins, PtdIns(3,4,5)P3] of PLC-γ; the PH domain [PtdIns(4,5)P2] and C2 domain (Ca2+) of PLC-δ; and the Ras binding domain (GTP-bound Ras) of PLC-∍. The presence of distinct regulatory domains in PLC isoforms renders them susceptible to different modes of activation. Given that the partners that interact with these regulatory domains of PLC isozymes are generated or eliminated in specific regions of the cell in response to changes in receptor status, the activation and deactivation of each PLC isoform are likely highly regulated processes. [3]
Evaluation of Phospholipase Activity in Biofilm Forming Candida Species Isolated from Intensive Care Unit Patients
Aims: To evaluate phospholipase activity in biofilm forming Candida spp. isolated from patients admitted in intensive care unit of rural tertiary care hospital.
Study Design: A total of 135 biofilm forming Candida spp. isolated from various clinical specimens of patients admitted in ICU were included in the study.
Place and Duration of Study: Department of Microbiology, Pravara Institute of Medical Science’s Rural Medical College India, between January 2010 and December 2012.
Methodology: The Candida isolates were identified upto species level by conventional standard mycological techniques. The biofilm formation was assessed by inoculating the isolates in conical polystyrene test tube containing Sabouraud’s dextrose broth supplemented with glucose. Phospholipase activity of biofilm forming Candida isolates was detected by using egg yolk agar.
Results: Out of 135 biofilm forming Candida spp. included in the study, 60 (44.4%) isolates were C. albicans. Among non-albicans Candida (NAC) spp. C. tropicalis was the major isolate followed by C. glabrata and C. parapsilosis. Phospholipase production was seen in 85 (62.9%) isolates. A total 49 (81.6%) isolates of C. albicans showed phospholipase activity. Among NAC spp. maximum phospholipase activity was seen in C. tropicalis and C. glabrata. [4]
Partial Purification and Characterization of Phospholipase A2 Inhibitor from Echis ocellatus Serum
The most effective and acceptable therapy for snakebite victims is the immediate administration of antivenin following envenomation which is limited by problems of hypersensitivity reactions in sensitive individuals and its inability to resolve the local effects of the venom. Phospholipase A2 Inhibitor from Echis ocellatus Serum (PIES) was isolated, partially purified and characterized. The neutralizing protein from E. ocellatus serum inhibited the E. ocellatus (carpet viper) venom phospholipase A2 (PLA2) enzyme in a dose dependent manner. A two step purification process on sephadex G-200 column chromatography and DEAE- cellulose chromatography gave an active fraction that inhibited the venom PLA2 by 78%. The result from SDS-PAGE showed the inhibitor to be a 24.98kDa protein and its kinetic study revealed a mixed pattern of inhibition on the carpet viper venom PLA2 with an estimated Ki values of 3.8%(v/v) to 7.3%(v/v). The study was carried out at the Department of Biochemistry, Faculty of Science, Ahmadu Bello University Zaria, Nigeria from June 2011 to August 2012. The relevance of these findings towards understanding the biochemistry of carpet viper envenomation and the development of a novel antivenin drug in future targeting the activity of PIES are discussed. [5]
Reference
[1] Yang, S.F., Freer, S. and Benson, A.A., 1967. Transphosphatidylation by phospholipase D. Journal of Biological Chemistry, 242(3), pp.477-484.
[2] Singer, W.D., Brown, H.A. and Sternweis, P.C., 1997. Regulation of eukaryotic phosphatidylinositol-specific phospholipase C and phospholipase D. Annual review of biochemistry, 66(1), pp.475-509.
[3] Rhee, S.G., 2001. Regulation of phosphoinositide-specific phospholipase C. Annual review of biochemistry, 70(1), pp.281-312.
[4] Deorukhkar, S. and Saini, S. (2013) “Evaluation of Phospholipase Activity in Biofilm Forming Candida Species Isolated from Intensive Care Unit Patients”, Microbiology Research Journal International, 3(3), pp. 440-447. doi: 10.9734/BMRJ/2013/4359.
[5] Adamude, F.A., Nok, A.J., Aliyu, N. and Onyike, E., 2016. Partial Purification and Characterization of Phospholipase A2 Inhibitor from Echis ocellatus Serum. International Journal of Biochemistry Research and Review, 13(1), pp.1-16.