Phosphatidylcholine-Preferring Phospholipase C from B. cereus. Function, Structure, and Mechanism

Abstract

The PLC class of enzymes has been studied extensively over the past 15-20 years because of their involvement in signaling pathways in which extracellular messages are delivered to the cell to induce a response. Of the PLC isoenzymes, the PI-PLCs have perhaps been examined in the greatest detail because of their key role in initiating cellular response by hydrolyzing the phosphodiester bond of phosphatidylinositols and their phosphorylated derivatives to release the second messengers IP 3 and DAG. However, the extended release of DAG that is critical to maintaining the stimulatory response arises from hydrolysis of the more abundant phosphatidylcholine by PC-PLC or by PLD followed by phosphatidic acid phosphatase. Because no eukaryotic PC-PLC has been cloned or isolated in pure form, the phosphatidylcholine-preferring PLC from B. cereus (PLC Bc ) has emerged as a focal point for investigation and as a putative model for mammalian PC-PLCs. The similarity of the active site of PLC Bc with other phosphoryl transfer enzymes has also served as a stimulus for mechanistic studies. The present account details recent studies of this important member of the PLC superfamily of enzymes.

Production and Characterization of Phospholipases C from some Bacillus thuringiensis Isolates Recovered from Egyptian Soil

“…Similar results were recorded by other researchers; Wang et al [37] found the maximum activity of PLC from B. mycoides to be at pH 7.0 -7.5. Hergenrother and Martin [5] reported that the optimal pH for activity of Bacillus cereus PLC was 8, while Otnaess et al [75] proved that the variation of pH from 7.2 to 8.3 affected neither activity nor substrate specificity of purified PLC from Bacillus cereus and the highest activity occurred at 37 to 60°C. Vis-à-vis, Durban et al [64] stated that the highest activity of PLC in the culture supernatants of 12 strains of Bacillus cereus against p-nitrophenylphosphorylcholine was at an acidic pH between 3.5 and 6 at 20 to 60°C.…”

“…Bacillus PLC is a 28.5 kDa enzyme whose structure has the three important features, the Zinc (Zn) centre consisting of three Zn ions that are all pentacoordinate; the choline binding site which is the substrate binding cleft that accommodates the choline headgroup and is lined with Glu4, Asp55, and Tyr56; and the lipid binding site [5]. In B. cereus group species, the transcriptional regulator PlcR (Phospholipase C Regulator) controls PLC production [6,7].…”

Recombinant broad-range phospholipase C from Listeria monocytogenes exhibits optimal activity at acidic pH

“…In this study, the L. monocytogenes broad-range PLC was cloned, expressed as an intein fused protein in Escherichia coli , purified, and characterized in an active and homogeneous form. Lm PLC orthologues from other Gram-positive bacteria, in particular the broad-range phospholipase C from Bacillus cereus ( Bc PLC) [11] and alpha-toxin from Clostridium perfringens [12], have been extensively characterized. Lm PLC shares considerable sequence (38.7%) and functional identity with Bc PLC, which binds three Zn 2+ ions at the enzyme active sites.…”

Diacylglycerol-Rich Domain Formation in Giant Stearoyl-Oleoyl Phosphatidylcholine Vesicles Driven by Phospholipase C Activity

“…The ability of DAG to induce nonbilayer phases is of crucial importance to its biological functions (Das and Rand, 1986). DAG is produced in the cell by phospholipase C via lipid hydrolysis (Hergenrother and Martin, 2001). The initial increase in DAG levels has been associated with the activity of the phosphatidylinositol-specific phospholipase C (PI-PLC) (Galneder et al, 2001), whereas prolonged elevation in DAG concentration is caused by the phosphatidylcholinepreferring phospholipase C (PC-PLC) (Exton, 1990).…”