Different possibilities for protein crosslinking are examined in this review, with special emphasis on enzymatic crosslinking and its impact on food structure. Among potential enzymes for protein crosslinking are transglutaminase (TG) and various oxidative enzymes. Crosslinking enzymes can be applied in cereal, dairy, meat, and fish processing to improve the texture of the product. Most of the current commercial applications are based on TG. The reaction mechanisms of the crosslinking enzymes differ, which in turn results in different technological properties.

Twenty-nine yeast strains were isolated from the ascocarps of black and white truffles (Tuber melanosporum Vitt. and Tuber magnatum Pico, respectively), and identified using a polyphasic approach. According to the conventional taxonomic methods, MSP-PCR fingerprinting and sequencing of the D1/D2 domain of 26S rDNA, the strains were identified as Candida saitoana, Debaryomyces hansenii, Cryptococcus sp., Rhodotorula mucilaginosa, and Trichosporon moniliiforme. All isolates assimilated L: -methionine as a sole nitrogen source and produced the volatile organic compounds (VOCs), 2-methyl butanol, 3-methyl butanol, methanethiol, S-methyl thioacetate, dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, dihydro-2-methyl-3(2H)-thiophenone and 3-(methylthio)-1-propanol (MTP). ANOVA analysis of data showed significant (P<0.01) differences in VOCs produced by different yeasts, with MTP as the major component (produced at concentrations ranging from 19.8 to 225.6 mg/l). In addition, since some molecules produced by the isolates of this study are also characteristic of truffle complex aroma, it is possible to hypothesize a complementary role of yeasts associated with this ecosystem in contributing to final Tuber spp. aroma through the independent synthesis of yeast-specific volatile constituents.

Laccases are copper‐containing enzymes used in various applications, such as textile bleaching. Several crystal structures of laccases from fungi and bacteria are available, but ascomycete types of fungal laccases (asco‐laccases) have been rather unexplored, and to date only the crystal structure of Melanocarpus albomyces laccase (MaL) has been published. We have now solved the crystal structure of another asco‐laccase, from Thielavia arenaria (TaLcc1), at 2.5 Å resolution. The loops near the T1 copper, forming the substrate‐binding pockets of the two asco‐laccases, differ to some extent, and include the amino acid thought to be responsible for catalytic proton transfer, which is Asp in TaLcc1, and Glu in MaL. In addition, the crystal structure of TaLcc1 does not have a chloride attached to the T2 copper, as observed in the crystal structure of MaL. The unique feature of TaLcc1 and MaL as compared with other laccases structures is that, in both structures, the processed C‐terminus blocks the T3 solvent channel leading towards the trinuclear centre, suggesting a common functional role for this conserved ‘C‐terminal plug’. We propose that the asco‐laccases utilize the C‐terminal carboxylic group in proton transfer processes, as has been suggested for Glu498 in the CotA laccase from Bacillus subtilis. The crystal structure of TaLcc1 also shows the formation of a similar weak homodimer, as observed for MaL, that may determine the properties of these asco‐laccases at high protein concentrations. Database 
Structural data are available in the Protein Data Bank database under the accession numbers http://www.rcsb.org/pdb/search/structidSearch.do?structureId=3PPS and http://www.rcsb.org/pdb/search/structidSearch.do?structureId=2VDZ Structured digital abstract  http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=nucleotide&cmd=Retrieve&dopt=Graphics&list_uids=$ http://www.ebi.ac.uk/ontology-lookup/?termId=MI:0407 to http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=nucleotide&cmd=Retrieve&dopt=Graphics&list_uids=$ by http://www.ebi.ac.uk/ontology-lookup/?termId=MI:0114 http://mint.bio.uniroma2.it/mint/search/interaction.do?interactionAc=MINT-8173385

Catechol oxidases (EC 1.10.3.1) catalyse the oxidation of o-diphenols to their corresponding o-quinones. These oxidases contain two copper ions (CuA and CuB) within the so-called coupled type 3 copper site as found in tyrosinases (EC 1.14.18.1) and haemocyanins. The crystal structures of a limited number of bacterial and fungal tyrosinases and plant catechol oxidases have been solved. In this study, we present the first crystal structure of a fungal catechol oxidase from Aspergillus oryzae (AoCO4) at 2.5-Å resolution. AoCO4 belongs to the newly discovered family of short-tyrosinases, which are distinct from other tyrosinases and catechol oxidases because of their lack of the conserved C-terminal domain and differences in the histidine pattern for CuA. The sequence identity of AoCO4 with other structurally known enzymes is low (less than 30 %), and the crystal structure of AoCO4 diverges from that of enzymes belonging to the conventional tyrosinase family in several ways, particularly around the central α-helical core region. A diatomic oxygen moiety was identified as a bridging molecule between the two copper ions CuA and CuB separated by a distance of 4.2-4.3 Å. The UV/vis absorption spectrum of AoCO4 exhibits a distinct maximum of absorbance at 350 nm, which has been reported to be typical of the oxy form of type 3 copper enzymes.