Laccases (EC 1.10.3.2) are "blue" copper-containing oxidoreductases widely distributed and highly important for biotechnology. The substrates of these enzymes are various phenolic compounds. Laccases are found in higher plants, some insects, fungi and bacteria. Laccases contain four copper atoms organized in 3 sites: Т1, Т2 и Т3. In bacteria, along with three-domain laccases, there are two-domain laccases (2DLac), which have a number of functional advantages. 2DLac are active at neutral and alkaline pH values, have increased thermostability and are resistant to the action of various inhibitors. The catalytic mechanism of the two-domain laccase is intensively studied; however, the principles of substrate/product transport are still not fully understood. This paper presents a comparative analysis of the catalytic activity and crystal structures of recombinant 2DLac from Streptomyces griseoflavus Ac-993 and its mutant forms with His165 substitutions on Phe and Ala. His165 is conservative for 2Dlac, it belongs to the second coordination sphere and is located near the surface of the protein. We assume that the movement of the imidazole ring His165 can "open" or "close" one of the substrate-product channels leading to the T2 /T3 center of laccase from S. griseoflavus.
two-domain laccases, Streptomyces griseoflavus, crystal structures, T2 / T3 center, substrates channels
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