## 4 Biochemical Properties of Lacase  
The suitability of enzyme proteins for biotechnological applications is determined by their biochemical properties, especially their stability in temperature and pH. Lacases are enzymes with diverse biochemical properties, depending on the type of organism synthesizing the enzyme. Bacterial lactose enzymes are mostly monomers with molecular masses in the range of 30 to 80 kDa. There are also a few subunit lacases in this group [21; 56]. The lacases mainly act intracellularly, although there are also extracellular lacases in this group of enzymes [57; 58; 59]. These enzymes are highly variable in their pH and temperature optima and often exhibit thermostability. Temperature optima, depending on the bacterial species, range from 25 to 85 \({}^{\circ}\)C. A similar trend is observed for pH optimum values. Bacterial lacases have been known to be active in acidic environments as well as in neutral and alkaline environments [18; 21]. For example, _A. lipoforum_ lactose shows the highest activity for syringaldazine at 70 at pH 6.0 [56], while _B. subtilis_\(\leq\) pH 3.0 at pH 7.0 for ABTS [60]. Under laboratory conditions, bacterial lactose shows activity against many substrates, including 2,4 dimethoxy phenol (_B. licheniformis_ LS04), azinobis(3-ethylbenzthiazoline-6-sulfonic acid, ABTS) (_Pseudomonas aeruginosa_), guiacol (_B. subtilis_), syringaldazine (_Stenrotrophomonas multophilia_) and hydroquinone (_P. desmyloticum_) [18; 58; 61; 62].  
Fungal lacases are among the best characterized. The stability of fungal lacases varies widely, depending on the source of origin. Typically, however, fungal lacases have lower thermal stability than bacterial lacases. It is likely that the stability has to do with the interaction of copper with the salt bridges, as well as hydrogen bonds that are part of the internal protein structures and the presence of certain amino acids [43; 57; 63]. These are overwhelmingly glycosylated enzymes that act extracellularly. The molecular weight of these enzymes typically ranges between 50 and 140 kDa. Most lacases purified from fungal cultures are monomeric proteins, but subunit enzymes have also been described [21; 40; 64]. The majority of fungal lacases are enzymes that operate in an acidic environment, with the optimum usually falling in the range of pH values 3-6, depending on the substrate. The temperature optimum for the activity of typical fungal lacases is between 50 and 70 \({}^{\circ}\)C [21; 64; 65]. In the case of fungal lacases, a frequently used substrate is ABTS or syringaldazine, which is often referred to as a specific substrate for lacases [66; 67].  
Laccases of plant and animal origin are less well described in the scientific literature. Plant lacases are glycoproteins secreted into the apoplast. Usually the molecular weight is between 60 and 150 kDa. The pH optimum is between 5 and 7. Plant lacase utilize typical lacase substrates, including ABTS, hydroquinone, catechol and 4-methylcatecholals [21; 40; 43; 68].  
Laccases are localized intracellularly in most insects, and their molecular weight ranges from 70 to 100 kDa. These enzymes show activity against ABTS, 4-methylcatechol, and dopamine and its derivatives as substrates [54; 67; 69; 70].  
Table 1 summarizes the biochemical properties for certain lacases of different origins.