NOVELTY - A new nucleic acid molecule comprises nucleic acid molecules that encode a polypeptide having the deduced amino acid sequence and having deacetylase activity.    USE - The nucleic acid molecule encoding a protein having deacetylase activity is useful for producing chitosan. The chitosan is useful for: (a) immobilization of enzymes and cells in biotechnology research and procedures; (b) strengthening and/or coloring of human and/or animal hair; (c) skin and/or nail care; (d) seed and/or crop protection and/or preservation; (e) adsorption of endotoxins and nucleic acids; (f) paper processing; or (g) as a polymer carrier for catalysts; an intermediate product for the synthesis of fine chemicals; an additive for whey feed; a composting accelerator; packing material; a clarifying means for juices; a flocculation agent; dietary fiber for foodstuff; food coating; wound dressing; surgical seam material; a dietetic additive for weight loss; contact lenses; nanoparticles for drug, gene or vaccine delivery; a loudspeaker diaphragm; an embedding medium for electron microscopy; a precipitant for waste water purification; or a catalyst in the production of N-acetylglucosamine from glucosamine. (All claimed.)    ADVANTAGE - The method of the invention provides high quality chitosans, i.e. chitosans with a well-defined degree of acetylation or a well-defined acetylation pattern.    DETAILED DESCRIPTION - The new nucleic acid molecule comprises: (1) nucleic acid molecules encoding a mature form of the polypeptide having the deduced amino acid sequence comprising a fully defined 234-amino acid sequence (SEQ ID No: 2); (2) nucleic acid molecules comprising the fully defined 750-bp sequence (SEQ ID No: 1), and encoding for a mature form of the polypeptide; (3) nucleic acid molecules encoding a fragment or derivative of a polypeptide encoded by a polynucleotide of (1) or (2), where in the derivative, one or more amino acid residues are conservatively substituted compared to the polypeptide, and the fragment or derivative has deacetylase activity; (4) nucleic acid molecules comprising a complementary strand which hybridizes under stringent conditions to a nucleic acid molecule in (1) to (3); (5) nucleic acid molecules which are at least 95% identical to a nucleic acid molecule in (1) to (4); (6) nucleic acid molecules which are at least 70% identical to a nucleic acid molecule in any one of (1) to (4); or (7) or the complementary strand of the nucleic acid molecule. The encoded protein has deacetylase activity. INDEPENDENT CLAIMS are:    (1) a method for producing a protein having deacetylase activity;    (2) an expression vector containing the nucleic acid molecule;    (3) a host cell transformed with the nucleic acid molecule or expression vector and serving as an expression system;    (4) a protein encoded by the nucleic acid molecule having a deacetylase activity;    (5) a method for producing chitosan from chitin, where N-acetylglucosamine-residues (GlcNAc) in a GlcNAc-Oligomer, GlcNAc-Polymer or chitin molecule are deacetylated with the protein;    (6) a method for producing chitosan, where GlcNAc-monomers are deacetylated with the protein in order to produce glucosamine (GlcN), which are then polymerized with untreated GlcNAc-monomers in order to obtain chitosan; and    (7) a method for producing N-acetylglucosamine from glucosamine, where the protein having deacetylase activity is used as a catalyst.