Lysozyme Activity

Topics: Lysozyme, Immune system, Innate immune system Pages: 6 (1902 words) Published: April 8, 2012
Lysozyme activity|
Observed in tears and saliva|
Connie Jamieson|


Lysozyme is an enzyme found in both tears and saliva. Each time we blink our eyes, our eyelids wash tears over the surface of our eyes. In addition, our mouth is continually producing saliva. A spectrophotometer set to 450nm was used to measure the effect of lysozyme on bacteria. The absorbance or optical density was measured for each sample at specific times with a total measuring time of twenty minutes. In this experiment, it was shown that lysozyme inhibits microbial growth in saliva and synthetic tears and in lysozyme standard control. The results showed a decrease in absorbance readings over time as the lysozyme activity was observed. Introduction

In 1922, Alexander Fleming caught a cold and a drop of nasal drainage fell from his nose into a Petri dish that happened to contain microorganisms [1]. He noticed there was a reaction between the bacteria and the fluid from his nose. Fleming realized the fluid contained a bacteriolytic element; he started his research to isolate this compound [1]. Later in 1922, Fleming named this compound lysozyme because of the lysing action on the observed microorganisms [1]. Fleming isolated the enzyme from the egg whites of a hen. After 1930, the bactericidal action of lysozyme was established and numerous studies conveyed that all living organisms produced lysozyme [1]. Tear lysozyme is a long chain glycolytic enzyme secreted by the lachrymal gland [3]. Lysozyme constitutes around twenty to forty percent of the total tear protein [3]. Its concentration in the tear is higher than in any other fluid of the body [1]. This protein has the ability to break down bacterial walls by the enzymatic digestion of mucopolysaccharides [4]. Because of this bactericidal action, lysozyme can be considered as one of the vital elements of the protective tear film barrier against ocular infection [5]. Innate immunity is an intricate sequence of responses that gives the body its first line of defense against infections [2]. The agents of innate immunity are always in place; when activated the innate immune system rapidly responds to threats [2]. The innate immune system, also called the nonspecific immune system does not discern between different infectious agents [2]. Physical barriers protect the body against the entrance of infectious microorganisms [2]. Physical barriers include the skin, the mucosal surfaces of the respiratory and gastrointestinal tract [2]. Lysozyme is an example of a biomolecule that participates in the innate immune response by its microbicidal effect on microorganisms [2]. These proteins also make effector molecules that are involved in inflammation and cell death [2]. Circulating cells like neutrophils also mediate the early inflammatory responses. They have granules that are filled with degradative enzymes similar to lysozyme and azurophilic granules, which are lysosomes [2]. These cytoplasmic granules of phagocytic cells can break down the petidoglycans in cell walls of gram-positive bacteria and few gram-negative bacteria [2]. The hypothesis for this experiment was lysozyme found in saliva, and synthetic tears will inhibit microbial growth.

Materials and method
500ul of diluted commercially prepared synthetic tears, normal saliva of two patients, and egg white lysozyme standard were mixed with 500ul of M. luteus suspended in a sp tryptic soy broth. The egg white lysozyme standard served as the positive control. PBS diluent was used to make 1:5 and 1:10 dilutions of synthetic tears, and 1:10 dilution of the egg white lysozyme standard. Using a spectrophotometer, the absorbance, or the optical density at 450nm was recorded at specific time intervals spanning twenty minutes. Time immediately started after the diluted lysozyme sample standard, diluted synthetic tears, and normal patient saliva were mixed with the M. luteus suspension....
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