Lysozyme activity in the presence of nonionic detergent micelles

Effects of ink characteristics and piezo-electric inkjetting parameters on lysozyme activity

Inkjet printing of enzymes can facilitate many novel applications where a small amount of materials need to be deposited in a precise and flexible manner. However, maintaining the satisfactory activity of inkjet printed enzyme is a challenging task due to the requirements of ink rheology and printhead parameters. Thus to find optimum inkjetting conditions we studied the effects of several ink formulation and jetting parameters on lysozyme activity using a piezoelectric printhead. Within linear activity range of protein concentrations ink containing 50 µg/mL lysozyme showed a satisfactory activity retention of 85%. An acceptable activity of jetted ink was found at pH 6.2 and ionic strength of 0.06 molar. Glycerol was found to be an effective viscosity modifier (10–15 mPa.s), humectant and protein structure stabilizer for the prepared ink. A non-ionic surfactant when used just below critical micelle concentration was found to be favourable for the jetted inks. An increase in activity retention was observed for inks jetted after 24 hours of room temperature incubation. However, no additional activity was seen for inkjetting above the room temperature. Findings of this study would be useful for formulating other protein-based inks and setting their inkjet printing parameters without highly compromising the functionality.

Clearing of suspensions of Micrococcus lysodeikticus catalysed by lysozymes from hen, goose, and turkey egg whites, human milk, and phage T4. Assessment of potential as signal generators for homogeneous enzyme immunoassays for urinary steroids

Lysozymes (3.2.1.17) from goose (Anser anser) egg white, turkey (Melagris gallopavo) egg white, phage T4 and human milk were compared with hen egg white lysozyme in their ability to clear a suspension of Micrococcus lysodeikticus. All of the lysozymes, except hen egg white lysozyme, catalysed the clearing of the Micrococcus lysodeikticus suspension in a biphasic fashion. Compared to hen egg white lysozyme, the total absorbance or transmission change over 5 and 20 minutes was less in all cases, except for human lysozyme. Human lysozyme was, therefore, a potential alternative, more rapid signal generator for the measurement of urinary estrone glucuronide excretion rates because of its structural similarity to hen egg white lysozyme. The apparent K(M) values for hen egg white lysozyme increased with the enzyme concentration.

Process-scale disruption of microorganisms

Common hosts for the large-scale manufacture of biological products, such as Escherichia coli and Saccharomyces cerevisiae, do not excrete products to the medium. Effective techniques for cell disruption are therefore required. These include physical, chemical, enzymatic and mechanical methods. Mechanical methods such as bead milling, high-pressure homogenization, and microfluidization are preferred. However, gentler, specific methods are receiving increasing attention particularly when used in combination to synergistically exploit their different specificities. Benefits can also be derived by integrating product release and recovery. In all cases it is essential to consider the interaction of the disruption operation with downstream units and to clearly demonstrate the cost benefits of alternative strategies.

The characterization and interconversion of three forms of cholesterol oxidase extracted from Nocardia rhodochrous

The physical properties and the methods used for interconversion of three forms of cholesterol oxidase extracted from Nocardia rhodochrous by treatment with Triton X-100, trypsin or buffer alone provide evidence that these forms differ chiefly in the possession or absence of a hydrophobic anchor region connected by a trypsin-sensitive region. The hydrophobic domain normally integrates the enzyme into the cell membrane and confers amphipathic properties on the solubilized enzyme, causing adsorption to hydrophobic resins, aggregation when detergent is removed and formation of mixed micelles with detergent and cholesterol resulting in surface-dilution kinetic behaviour and activation by relatively high concentrations of water-miscible solvents. By contrast, only the enzymic fragment is extracted with trypsin and it behaves as a conventional soluble enzyme and does not aggregate or interact with hydrophobic resins, detergents or water-miscible solvents. As no phospholipid could be detected in the enzyme extracts, the detergent appears to act as a substitute for the cell-membrane lipids that would normally interact with the hydrophobic region. This cholesterol oxidase is an example of a prokaryotic enzyme possessing two closely associated catalytic functions, dehydrogenase and isomerase activities, and an anchoring function.

The inhibition of lysozyme by bile acids

The effect of bile acids on the bacteriolytic activity of lysozyme towards Micrococcus lysodeikticus was studied in vitro. All bile acids tested inhibited lysozyme activity. Conjugated bile acids were better inhibitors than their unconjugated homologs and sulfation resulted in still stronger inhibition. A study of UV-difference spectra of bile acid-lysozyme mixtures suggests that bile acids distort the tertiary structure of the enzyme. The inhibition-concentration curves of micelle-forming bile acids were bell-shaped, and peak inhibition was apparently related to the critical micellar concentration. The inhibition-concentration curves of sulfated bile acids, which do not form micelles, are characterized by a plateau of maximal inhibition. A mechanism of lysozyme activation by bile acid micelles is proposed. Our results illustrate the complex interactions between antibacterial compounds in the gut. As bile acids are known to inhibit lipase activity as well, these studies suggest that bile acids may have an important influence on intestinal enzyme activity in general.