Lysozymi

Lysozymi, or lysozymes, are small enzymes that cleave the polysaccharide backbone of bacterial cell walls. They catalyze the hydrolysis of β-(1,4)-glycosidic bonds between N-acetylglucosamine and N-acetylmuramic acid in peptidoglycan, weakening the cell wall and often causing bacterial lysis. A typical lysozyme is about 14 kilodaltons in mass and contains 129 amino acids. In chicken egg-white lysozyme, the catalytic dyad consists of Glu35 and Asp52, positioned in a compact, highly stable structure.

Lysozymi are found in a variety of secretions and tissues; notable sources include egg white, tears, saliva, and mucus. They belong mainly to the c-type lysozymes family, with other forms such as goose-type (g-type) lysozymes identified in some species. The mature enzyme is stabilized by multiple disulfide bonds and folds into a single, compact domain enriched in beta sheets and alpha helices.

Activity and spectrum of activity vary by lysozyme type and organism. They are typically more effective against Gram-positive bacteria, which present exposed peptidoglycan, while Gram-negative bacteria are less susceptible due to the outer membrane barrier; however, lysozymes can act synergistically with other antimicrobial agents and conditions. Some lysozymes also exhibit antiviral or antifungal effects in certain contexts. Beyond biology, lysozymi serve as important model enzymes in studies of catalysis, protein folding, and stability.

History and significance: Lysozyme was discovered by Alexander Fleming in 1922 in Staphylococcus cultures. Its structure and mechanism were elucidated in the 1960s, with early high-resolution structures obtained by X-ray crystallography. Today, lysozymi are widely used in biochemistry education, food preservation, and various research applications.