ABSTRACT
The most comprehensive studies on a plant lysozyme (EC 3.2.1.17) are those on the enzyme from papaya (Carica papaya) latex, published in 1967 and 1969. However, the N-terminal amino acid sequence of five amino acid sequence of this enzyme, determined by manual Edman degradation, did not allow assignment to any of the much later-classified families of glycosyl hydrolases. N-Terminal sequence analysis of 22 residues of papaya lysozyme now shows unambiguously that the enzyme belongs to the family 19 chitinases. It has properties similar to those of basic class I chitinases with lysozyme activity, such as cleavage specificity at the C-1 of N-acetylmuramic acid with inversion of configuration, but as it lacks an N-terminal hevein domain, it should be classified as a class II chitinase.
