Engineering of the nonspecific phospholipase C from Bacillus cereus: replacement of glutamic acid-4 by alanine results in loss of interfacial catalysis and enhanced phosphomonoesterase activity

Recombinant Lipases and Phospholipases and Their Use as Biocatalysts for Industrial Applications

Lipases and phospholipases are interfacial enzymes that hydrolyze hydrophobic ester linkages of triacylglycerols and phospholipids, respectively. In addition to their role as esterases, these enzymes catalyze a plethora of other reactions; indeed, lipases also catalyze esterification, transesterification and interesterification reactions, and phospholipases also show acyltransferase, transacylase and transphosphatidylation activities. Thus, lipases and phospholipases represent versatile biocatalysts that are widely used in various industrial applications, such as for biodiesels, food, nutraceuticals, oil degumming and detergents; minor applications also include bioremediation, agriculture, cosmetics, leather and paper industries. These enzymes are ubiquitous in most living organisms, across animals, plants, yeasts, fungi and bacteria. For their greater availability and their ease of production, microbial lipases and phospholipases are preferred to those derived from animals and plants. Nevertheless, traditional purification strategies from microbe cultures have a number of disadvantages, which include non-reproducibility and low yields. Moreover, native microbial enzymes are not always suitable for biocatalytic processes. The development of molecular techniques for the production of recombinant heterologous proteins in a host system has overcome these constraints, as this allows high-level protein expression and production of new redesigned enzymes with improved catalytic properties. These can meet the requirements of specific industrial process better than the native enzymes. The purpose of this review is to give an overview of the structural and functional features of lipases and phospholipases, to describe the recent advances in optimization of the production of recombinant lipases and phospholipases, and to summarize the information available relating to their major applications in industrial processes.

High level expression of a recombinant phospholipase C from Bacillus cereus in Bacillus subtilis

Twenty-two Bacillus cereus strains were screened for phospholipase C (PLC, EC 3.1.4.3) activity using p-nitrophenyl phosphorylcholine as a substrate. Two strains (B. cereus SBUG 318 and SBUG 516) showed high activity at elevated temperatures (>70 degrees C) at acidic pH (pH 3.5-6) and were selected for cloning and functional expression using Bacillus subtilis. The genes were amplified from B. cereus DNA using primers based on a known PLC sequence and cloned into the expression vector pMSE3 followed by transformation into B. subtilis WB800. On the amino acid level, one protein (PLC318) was identical to a PLC described from B. cereus, whereas PLC516 contained an amino acid substitution (E173D). PLC production using the recombinant strains was performed by an acetoin-controlled expression system. For PLC516, 13.7 U g(-1) wet cell weight was determined in the culture supernatant after 30 h cultivation time. Three purification steps resulted in pure PLC516 with a specific activity of 13,190 U mg(-1) protein.

Probing Polyethylene Glycol-Phospholipid Membrane Interactions Using Enzymes

Interaction of polyethylene glycols (PEGs) with phospholipid membranes leads to aggregation and fusion of membranes. The structural basis of these events in membranes, especially in contact with low-molecular-weight PEGs, is uncertain. Using phsopholipases, a class of interfacially active enzymes, we demonstrate enhanced accessibility of lipid hydrophobic portions in the presence of PEGs. All three phospholipases, i.e., A(2), C, and D, show enhancement of activity in the presence of PEGs. Enhancement of activity does not depend on the size of the vesicle or the presence of proteins in the membrane. Fluorescence quenching of probes buried in the membrane supports the phospholipase data. The utility of phospholipases as probes to monitor local and fine structural changes in the membranes is discussed. Copyright 1999 Academic Press.

Comparison of dynamic and integrated light-scattering techniques in the study of the interaction of Candida rugosa lipase with DPPC liposomes

Dynamic light-scattering (DLS) and wide angle integrated light-scattering (WAILS) spectroscopies were evaluated in the study of binding of Candida rugosa lipase (CRL) with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes. The use of cumulants analysis on DLS data allowed for the determination of general lipase-liposome-binding trends. Particle intensity distributions obtained from DLS data by a discrete inversion method revealed the different populations created upon lipase-liposome interactions. Using a discrete inversion technique on WAILS data, not only these populations could be differentiated but also accurate number distributions were obtained in short periods of time. Both DLS and WAILS are excellent tools for the study of lipase binding to lipid vesicles; however, care must be exercised in the analysis of the experimental data whenever particle size distributions are multimodal. The selection of the light scattering technique will depend on the information required.

Modulation of enzymatic activity and biological function of Listeria monocytogenes broad-range phospholipase C by amino acid substitutions and by replacement with the Bacillus cereus ortholog

The secreted broad-range phosphatidylcholine (PC)-preferring phospholipase C (PC-PLC) of Listeria monocytogenes plays a role in the bacterium's ability to escape from phagosomes and spread from cell to cell. Based on comparisons with two orthologs, Clostridium perfringens alpha-toxin and Bacillus cereus PLC (PLCBc), we generated PC-PLC mutants with altered enzymatic activities and substrate specificities and analyzed them for biological function in tissue culture and mouse models of infection. Two of the conserved active-site zinc-coordinating histidines were confirmed by single amino acid substitutions H69G and H118G, which resulted in proteins inactive in broth culture and unstable intracellularly. Substitutions D4E and H56Y remodeled the PC-PLC active site to more closely resemble the PLCBc active site, while a gene replacement resulted in L. monocytogenes secreting PLCBc. All of these mutants yielded similar amounts of active enzyme as wild-type PC-PLC both in broth culture and intracellularly. D4E increased activity on and specificity for PC, while H56Y and D4E H56Y showed higher activity on both PC and sphingomyelin, with reduced specificity for PC. As expected, PLCBc expressed by L. monocytogenes was highly specific for PC. During early intracellular growth in human epithelial cells, the D4E mutant and the PLCBc-expressing strain performed significantly better than the wild type, while the H56Y and D4E H56Y mutants showed a significant defect. In assays for cell-to-cell spread, the H56Y and D4E mutants had close to wild-type characteristics, while the spreading efficiency of PLCBc was significantly lower. These studies emphasize the species-specific features of PC-PLC important for growth in mammalian cells.