Biotransformation of hydroquinone into α-arbutin by transglucosylation activity of a metagenomic amylosucrase

Tricholoma matsutake polysaccharides suppress excessive melanogenesis via JNK-mediated pathway: Investigation in 8- methoxypsoralen induced B16-F10 melanoma cells and clinical study

Skin hyperpigmentation is a worldwide condition associated with augmented melanogenesis. However, conventional therapies often entail various adverse effects. Here, we explore the safety range and depigmentary effects of polysaccharides extract of Tricholoma matsutake (PETM) in an in vitro model and further evaluated its efficacy at the clinical level. An induced-melanogenesis model was established by treating B16-F10 melanoma cells with 8-methoxypsoralen (8-MOP). Effects of PETM on cell viability and melanin content were examined and compared to a commonly used depigmentary agent, α-arbutin. Expressions of key melanogenic factors and upstream signaling pathway were analysed by quantitative PCR and western blot. Moreover, a placebo-controlled clinical study involving Chinese females with skin hyperpigmentation was conducted to measure the efficacy of PETM on improving facial pigmented spots, melanin index, and individual typology angle (ITA°). Results demonstrated that PETM (up to 0.5 mg/mL) had little effect on the viability and motility of B16-F10 cells. Notably, it significantly suppressed the melanin content and expressions of key melanogenic factors induced by 8-MOP in B16-F10 melanoma cells. Western blotting results revealed that PETM inhibited melanogenesis by inactivating c-Jun N-terminal kinase (JNK), and this inhibitory role could be rescued by JNK agonist treatment. Clinical findings showed that PETM treatment resulted in a significant reduction of facial hyperpigmented spot, decreased melanin index, and improved ITA° value compared to the placebo-control group. In conclusion, these in vitro and clinical evidence demonstrated the safety and depigmentary efficacy of PETM, a novel polysaccharide agent. The distinct mechanism of action of PETM on melanogenic signaling pathway positions it as a promising agent for developing alternative therapies.

Immobilization of Thermomyces lanuginosus lipase in a novel polysaccharide-based hydrogel by a two-step crosslinking method and its use in the lauroylation of α-arbutin

The Thermomyces lanuginosus lipase (TLLs) was successfully immobilized within a novel hydrogel matrix through a two-step crosslinking method. TLLs were initially crosslinked through the Schiff base reaction by oxidized carboxymethyl cellulose (OCMC). The water-soluble OCMC@TLLs complex was subsequently crosslinked by carboxymethyl chitosan (CMCSH) in a microfluidic apparatus to form the CMCHS/OCMC@TLLs microspheres. The CD (Circular Dichroism, CD) and FT-IR (Fourier Transform infrared spectroscopy, FT-IR) spectra demonstrated that the crosslinking of TLLs with OCMC resulted in a less significant impact on their structure compared to that with glutaraldehyde. CMCHS/OCMC@TLLs showed decreased catalytic performance due to the mass transfer resistance, while its thermal stability was greatly improved. The CMCHS/OCMC@TLLs were used to catalyze the lauroylation of arbutin in tetrahydrofuran. After 12 h of reaction under optimal conditions, the yield of 6'-O-lauryl arbutin reached an impressive 92.12%. The prepared 6'-O-lauryl arbutin has high lipophilicity and exhibits similar tyrosinase inhibitory activity and higher antioxidant activity compared to its parent compound.

Characterization of a novel sucrose phosphorylase from Paenibacillus elgii and its use in biosynthesis of α-arbutin

α-Arbutin, a naturally occurring glycosylated derivative of hydroquinone (HQ), effectively inhibits melanin biosynthesis in epidermal cells. It is widely recognized as a fourth-generation whitening agent within the cosmetic industry. Currently, enzymatic catalysis is universally deemed the safest and most efficient method for α-arbutin synthesis. Sucrose phosphorylase (SPase), one of the most frequently employed glycosyltransferases, has been extensively reported for α-arbutin synthesis. In this study, a previously reported SPase known for its effectiveness in synthesizing α-arbutin, was used as a probe sequence to identify a novel SPase from Paenibacillus elgii (PeSP) in the protein database. The sequence similarity between PeSP and the probe was 39.71%, indicating a degree of novelty. Subsequently, the gene encoding PeSP was coexpressed with the molecular chaperone pG-Tf2 in Escherichia coli, significantly improving PeSP's solubility. Following this, PeSP was characterized and employed for α-arbutin biosynthesis. The specific activity of co-expressed PeSP reached 169.72 U/mg, exhibited optimal activity at 35℃ and pH 7.0, with a half-life of 3.6 h under the condition of 35℃. PeSP demonstrated excellent stability at pH 6.5-8.5 and sensitivity to high concentrations of metal ions. The kinetic parameters Km and kcat/Km were determined to be 14.50 mM and 9.79 min- 1·mM- 1, respectively.The reaction conditions for α-arbutin biosynthesis using recombinant PeSP were optimized, resulting in a maximum α-arbutin concentration of 52.60 g/L and a HQ conversion rate of 60.9%. The optimal conditions were achieved at 30℃ and pH 7.0 with 200 U/mL of PeSP, and by combining sucrose and hydroquinone at a molar ratio of 5:1 for a duration of 25 h.

Research progress and application of enzymatic synthesis of glycosyl compounds

Glucoside compounds are widely found in nature and have garnered significant attention in the medical, cosmetics, and food industries due to their diverse pharmaceutical properties, biological activities, and stable application characteristics. Glycosides are mainly obtained by direct extraction from plants, chemical synthesis, and enzymatic synthesis. Given the challenges associated with plant extraction, such as low conversion rates and the potential for environmental pollution with chemical synthesis, our review focuses on enzymatic synthesis. Here, we reviewed the enzymatic synthesis methods of 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G), 2-O-α-D-glucosyl glycerol (α-GG), arbutin and α-glucosyl hesperidin (Hsp-G), and other glucoside compounds. The types of enzymes selected in the synthesis process are comprehensively analyzed and summarized, as well as a series of enzyme transformation strategies adopted to improve the synthetic yield. KEY POINTS: • Glycosyl compounds have applications in the biomedical and food industries. • Enzymatic synthesis converts substrates into products using enzymes as catalysts. • Substrate bias and specificity are key to improving substrate conversion.

Recent trends in the modification of polyphenolic compounds using hydroxylation and glycosylation

Polyphenols are bioactive molecules that are used in therapeutics. Polyphenol hydroxylation and glycosylation have been shown to increase their bioavailability, solubility, bioactivity, and stability for use in various applications. Ortho-hydroxylation of polyphenols using tyrosinase allows high selectivity and yield without requiring a cofactor, while meta- and para-hydroxylation of polyphenols are mediated by site-specific hydroxylases and cytochrome P450s, although these processes are somewhat rare. O-glycosylation of polyphenols proceeds further after hydroxylation. The O-glycosylation reaction typically requires nucleotide diphosphate (NDP) sugar. However, amylosucrase (AS) has emerged as a promising enzyme for polyphenol glycosylation in large-scale production without requiring NDP-sugar. Overall, this review describes recent findings on the enzymatic mechanisms, enzyme engineering, and applications of enzymatic reactions.

Combinatorial metabolic engineering enables high yield production of α-arbutin from sucrose by biocatalysis

α-Arbutin has been widely used as a skin-whitening ingredient. Previously, we successfully produced α-arbutin via whole-cell biocatalysis and found that the conversion rate of sucrose to α-arbutin was low (~45%). To overcome this issue, herein, we knocked out the genes of enzymes related to the sucrose hydrolysis, including sacB, sacC, levB, and sacA. The sucrose consumption was reduced by 17.4% in 24 h, and the sucrose conversion rate was increased to 51.5%. Furthermore, we developed an inducible protein degradation system with Lon protease isolated from Mesoplasma florum (MfLon) and proteolytic tag to control the PfkA activity, so that more fructose-6-phosphate (F6P) can be converted into glucose-1-phosphate (Glc1P) for α-arbutin synthesis, which can reduce the addition of sucrose and increase the sucrose conversion efficiency. Finally, the pathway of F6P to Glc1P was enhanced by integrating another copy of glucose 6-phosphate isomerase (Pgi) and phosphoglucomutase (PgcA); a high α-arbutin titer (~120 g/L) was obtained. The sucrose conversion rate was increased to 60.4% (mol/mol). In this study, the substrate utilization rate was boosted due to the attenuation of its hydrolysis and the assistance of the intracellular enzymes that converted the side product back into the substrate for α-arbutin synthesis. This strategy provides a new idea for the whole-cell biocatalytic synthesis of other products using sucrose as substrate, especially valuable glycosides.Key points The genes of sucrose metabolic pathway were knocked out to reduce the sucrose consumption. The by-product fructose was reused to synthesize α-arbutin. The optimized whole-cell system improved sucrose conversion by 15.3%.

Recent Progress on Feasible Strategies for Arbutin Production

Arbutin is a hydroquinone glucoside and a natural product present in various plants. Arbutin potently inhibits melanin formation. This property has been exploited in whitening cosmetics and pharmaceuticals. Arbutin production relies mainly on chemical synthesis. The multi-step and complicated process can compromise product purity. With the increasing awareness of sustainable development, the current research direction prioritizes environment-friendly, biobased arbutin production. In this review, current strategies for arbutin production are critically reviewed, with a focus on plant extraction, chemical synthesis, biotransformation, and microbial fermentation. Furthermore, the bottlenecks and perspectives for future direction on arbutin biosynthesis are discussed.