Lysozyme, hydrochloride

Endpoint summary

Additional information

No specific information exists on the toxicity of lysozyme hydrochloride to aquatic life. However lysozyme hydrochloride is naturally occurring in many organisms, including aquatic organisms (mucus, lymphoid tissue, plasma and other body fluids of freshwater and marine fish); it is also expressed in a wide variety of their tissues (Saurabh and Saho, 2008). Bivalve mollusc employs different lysozymes for different functions (Xue et al., 2007).

Important factors that may impact on the aquatic system are pH, temperature, air- and photo-stability; heating, dilution, mixing of solutions with air, etc, lead to denaturation of the enzyme, i.e. loss of the enzymatic activity. In fact, enzymes are sensitive to changes in the previous mentioned conditions and they undergo to rapid unfolding process (changes in the three-dimensional structure), which facilitates the proteolytic degradation. Considering the common chemical features of enzymes and their general evaluation as substances easily accessible to biodegradation, it is expected that these materials are rapidly and ultimately biodegraded in the environment.

For completeness sake, the acute toxicity has been investigated on the base of the comparison with other enzymes, specifically, lipase, cellulase and Subtilisins (Protease): according to the Enzyme Commission (EC) classification, they are all subcategorized as hydrolases enzymes acting on ester bonds in the case of lipase, acting on the peptide bonds (peptidases) and acting as glycosylases in the cases of cellulase and lysozyme. In all cases, the enzymes resulted ready biodegradable, as expected considering their globular protein structure.

Data are available on the three trophic levels, i.e. algae, invertebrates and fish. The analyses have not revealed either significant toxic effects, or reasons of concern. Data evaluated as reliable are consistent and characterize the enzymes as non-toxic to aquatic life. Since available data are not specific for Lysozyme, it is preferred to make a qualitative assessment.

In the chronic exposure context, it has to be considered that enzymes are proteins, hydrophilic and readily biodegradable; in nature, they are involved at any level of the food chain and in the microbial biodegradation. All enzyme classes are readily biodegradable and degradation products are primarily peptides and amino acids, followed by carbon dioxide and water which cause no harm to nature.

On the basis of the rapid elimination from the eco-systems, long-term testing can be considered less relevant.

Moreover the bioconcentration can generally be neglected, due to the hydrophilic properties and ready biodegradability of proteins. Additionally, lysozyme is naturally present in the environment and in case releases would occured, they would be minimal in relation to natural background concentrations.

REFERENCE

Saurabh S. and Sahoo P K (2008). Lysozyme: an important defence molecule of fish innate immune system. Aquaculture Research, 39, 223 - 239

Xue QG, Itoh N., Schey KL, Li YL, Cooper RK, La Peyre JF (2007). A new lysozyme from the eastern oyster (Crassostrea virginica) indicates adaptive evolution of i-type lysozymes. Cell Mol Life Sci. Jan;64(1):82-95.