Sequence analysis of grape (Vitis vinifera) berry chitinases that cause haze formation in wines

Chitinases account for ca. 50% of the soluble proteins in the berries of th e grape vine (Vitis vinifera L. Muscat of Alexandria). The other major prot eins present are thaumatin-like proteins. Both these groups of proteins per sist through the vinification process and cause hazes and sediments in bott led wines. Four chitinases have been purified from Muscat of Alexandria fru it and characterized by both sequence and mass spectral analysis. Their pro tein sequences were highly similar, and all proteins were modified at their N-terminus. It was confirmed for three of the chitinases that the N-termin al group was a pyroglutamate residue. Comparative sequence analysis of two chitinases from berries and two from wine demonstrated that, despite their reputed resistance to proteolytic degradation, some limited proteolytic pro cessing of these proteins occurs. The peptide fragments of the chitinases a ccount for only 3% of the total soluble protein content of the fruit.