Enzymatic synthesis of bioactive compounds by Rhus laccase from Chinese Rhus vernicifera

Abstract

A simple one step synthesis of pinoresinol and its derivatives-active components of Du-Zhong (Eucommia ulmoides)-from coniferyl alcohol and p-courmaryl alcohol with higher yields was achieved by Rhus laccases (RL) catalysis in water miscible organic solvents. Biomacromolecules dehydrogenative polymers (DHP) were only synthesized by fungal laccases, not by RL. The structures and the reaction mechanism were discussed to promote the understanding of the function of laccases in the process of lignin biosynthesis.lignan, laccases, pinoresinol, dehydrogenative polymers, enzymatic mechanism Lignans and neolignans, consisting of two phenylpropanoid units (Figure 1), are widely distributed in plants [1][2][3][4] . Although phillyrin and pinoresinol, kinds of lignan analog, were separated by Carboncini in 1863 and Bamberger in 1894 respectively, they had not been taken seriously until podophyllotoxin analogue-Eptoside was used as an anticancer drug in the seventies of the last century [5][6][7] . Now podophyllotoxin, pinoresinol and its derivatives (active components of Du-Zhong [Eucommia ulmoides], a Chinese herbal medicine which has been used for several thousand years in China [8] due to its nontoxicity and antihypertensive activity) and other lignan compounds are used in cancer chemotherapy, antiviral and antimicrobial applications, and antioxidation, having the functions of inhibiting cAMP phosphodiesterase activities, toxicity of a wide variety of insecticides and antihypertensive activity, etc. [2,3,7,[9][10][11] .Recently, increasing interests have been put on the application of laccases (EC 1.10.3.2, p-diphenol: dioxygen oxidoreductase) as a new biocatalyst in organic synthesis because environmentally friendly oxidation has become a very important field in green chemistry [12,13] . Rhus laccase (RL) purified from the Chinese peculiar plant Rhus vernicifera, however, was often criticized due to its low activity [14 -17] . Though various methods were tried and efforts were made to improve its activity, no obvious efficacy could be observed. Can't the disadvantage be used of directly?In this work, various substrates catalyzed by Rhus laccases (RL), which were separated from the Chinese peculiar plant Rhus vernicifera, were investigated. Two fungal laccases from Pycnoporus coccineus (PCL) and Trametes spec (TL) were also discussed in order to make a comparison with RL in water miscible solvents.

Enzymatic catalysis of 2,6-dimethoxyphenol by laccases and products characterization in organic solutions

“…3515 cm −1 does not appear. It is another example for RL to be used for the synthesis of special small molecules although it shows lower activity while PCL shows stronger catalyzed ability for higher polymers [18] . The various enzymatic activities of RL and PCL could be the reason for the difference of their catalyzed products.…”

“…Compared with fungal laccases which have been studied thoroughly and extensively [9,[11][12][13] , plant laccases, such as Rhus laccases (RL) which were isolated from the sap of Chinese lacquer tree (Rhus vernicifera) [14] , have only been marginally evaluated [3,[15][16][17] and it is still worthwhile to study the enzymatic activity of RL in various solvents, especially in nonaqueous solvents with the appreciated advantages [18] . This kind of will facilitate the investigation of the reaction mechanisms of phenolic substrates, such as urushiol and dioxins, which are insoluble or poorly soluble in water.…”

Application of Pyrolysis Gas Chromatography/Mass Spectrometry in Lacquer Research: A Review

“…As it is very important to investigate the process of functional expression in coating material science, Niimura and Miyakoshi examined the functional expression of Asian lacquer film by Py-GC/MS during the hardening process and found that Asian lacquer develops an extreme hardness and insolubility by accelerating nucleus-side chain (C-C, C-O-C) and side chain-side chain (C-C) cross-linkages [54]. Py-GC/MS also was used to confirm the structure of a laccase-catalyzed reaction [55,56]. Recently, on-line micro-ultraviolet pyrolysis GC/MS [57], evolved gas analysis-ion [58], and thermogravimetry-linked scan mass spectrometry [59] were used to analyze ancient lacquer wares, and then the results were compared with standard lacquer films.…”

Mechanism of monolignol biotransformation by Rhus laccases in water-miscible organic solutions

“…Lignans are closely related to lignins, both of which are assembled from the same simple phenolic precursors. Together they play important roles in plant defense and cell wall reinforcement: the lignans have antimicrobial, antifungal, antiviral, and antioxidant properties [2], and the lignins play structural roles in supporting vascular apparatus integrity, making the plant cells impermeable to water, allowing water conduction, giving rigidity against compressive forces, and serving as a mechanical barrier against pathogens.…”

“…It was found that RL had optimal activity [18] in a water/glycerin mixture [19], and that coniferyl alcohol was catalyzed by RL in a water/acetone solution, although the reaction was slow [2,20]. RL is a very important model enzyme [21] and in this paper mainly the mechanism of enzyme catalysis of lignin precursors in organic solvent/water (O/W) systems is discussed based on our previously published works [2,18,20]. Factually, in active resin duct plant enzymes are just immersed in O/W system and therefore this mechanism investigation is authentic on the basis process of nature enzymatic catalysis.…”