Abstract
Abstract A procedure is described for the isolation of fig lysozyme from dried fig latex. The pure enzyme has a molecular weight of 29,000 and consists of a single polypeptide chain with amino-terminal glycine and carboxyl-terminal isoleucine residues. With Micrococcus lysodeikticus cells as substrate, the enzyme exhibits a sharp pH optimum at pH 4.5. Fig lysozyme is considerably more active toward chitin and tetra-N-acetyl-d-glucosamine than egg-white lysozyme. The enzyme shows a strong ionic strength dependence, maximal activity being attained at an ionic strength of 0.02 to 0.03. The physical and enzymatic properties of fig lysozyme are strikingly similar to those of papaya lysozyme, although the amino acid compositions of the two enzymes show many differences. Fig lysozyme, just as papaya and egg-white lysozymes, is powerfully inhibited by histamine. A mechanism for this inhibition is suggested.
Highlights
A procedure has been developed for the preparation of fig lysozyme, in pure form, free from contaminating proteolytic activity
This enzyme has been characterized with respect to its amino acid composition, amino- and carboxylterminal residues, molecular weight, and enzymatic properties
The pH-activity profile a ith chitin, a neutral substrate, indicated that groups with similar pK values were involved in the catalysis by both the egg-white and papaya enzymes [3,6]
Summary
A procedure is described for the isolation of Cg lysozyme from dried fig latex. The pure enzyme has a molecular weight of 29,000 and consists of a single polypeptide chain with amino-terminal glycine and carboxyl-terminal isoleucine residues. This is of particular interest, since many similarities have been shown to exist between the proteolytic enzymes of plant &ices [12, 13] For these reasons, a procedure has been developed for the preparation of fig lysozyme, in pure form, free from contaminating proteolytic activity. A procedure has been developed for the preparation of fig lysozyme, in pure form, free from contaminating proteolytic activity This enzyme has been characterized with respect to its amino acid composition, amino- and carboxylterminal residues, molecular weight, and enzymatic properties. The pH-activity profile a ith chitin, a neutral substrate, indicated that groups with similar pK values were involved in the catalysis by both the egg-white and papaya enzymes [3,6] This suggests that the enzymes have a similar mechanism of glycosidic bond hydrolysis.
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