Enhanced chemoselectivity of a plant cytochrome P450 through protein engineering of surface and catalytic residues

Recent advancements in mogrosides: A review on biological activities, synthetic biology, and applications in the food industry

Mogrosides are low-calorie, biologically active sweeteners that face high production costs due to strict cultivation requirements and the low yield of monk fruit. The rapid advancement in synthetic biology holds the potential to overcome this challenge. This review presents mogrosides exhibiting antioxidant, anti-inflammatory, anti-cancer, anti-diabetic, and liver protective activities, with their efficacy in diabetes treatment surpassing that of Xiaoke pills (a Chinese diabetes medication). It also discusses the latest elucidated biosynthesis pathways of mogrosides, highlighting the challenges and research gaps in this field. The critical and most challenging step in this pathway is the transformation of mogrol into a variety of mogrosides by different UDP-glucosyltransferases (UGTs), primarily hindered by the poor substrate selectivity, product specificity, and low catalytic efficiency of current UGTs. Finally, the applications of mogrosides in the current food industry and the challenges they face are discussed.

Deep learning-based characterization and redesign of major potato tuber storage protein

Potato is one of the most important crops worldwide, to feed a fast-growing population. In addition to providing energy, fiber, vitamins, and minerals, potato storage proteins are considered as one of the most valuable sources of non-animal proteins due to their high essential amino acid (EAA) index. However, low tuber protein content and limited knowledge about potato storage proteins restrict their widespread utilization in the food industry. Here, we report a proof-of-concept study, using deep learning-based protein design tools, to characterize the biological and chemical characteristics of patatins, the major potato storage proteins. This knowledge was then employed to design multiple cysteines on the patatin surface to build polymers linked by disulfide bonds, which significantly improved viscidity and nutrient of potato flour dough. Our study shows that deep learning-based protein design strategies are efficient to characterize and to create novel proteins for future food sources.

Engineering of CYP82Y1, a cytochrome P450 monooxygenase: a key enzyme in noscapine biosynthesis in opium poppy

Protein engineering provides a powerful base for the circumvention of challenges tied with characteristics accountable for enzyme functions. CYP82Y1 introduces a hydroxyl group (-OH) into C1 of N-methylcanadine as the substrate to yield 1-hydroxy-N-methylcanadine. This chemical process has been found to be the gateway to noscapine biosynthesis. Owning to the importance of CYP82Y1 in this biosynthetic pathway, it has been selected as a target for enzyme engineering. The insertion of tags to the N- and C-terminal of CYP82Y1 was assessed for their efficiencies for improvement of the physiological performances of CYP82Y1. Although these attempts achieved some positive results, further strategies are required to dramatically enhance the CYP82Y1 activity. Here methods that have been adopted to achieve a functionally improved CYP82Y1 will be reviewed. In addition, the possibility of recruitment of other techniques having not yet been implemented in CYP82Y1 engineering, including the substitution of the residues located in the substrate recognition site, formation of the synthetic fusion proteins, and construction of the artificial lipid-based scaffold will be discussed. Given the fact that the pace of noscapine synthesis is constrained by the CYP82Y1-catalyzing step, the methods proposed here are capable of accelerating the rate of reaction performed by CYP82Y1 through improving its properties, resulting in the enhancement of noscapine accumulation.

Progress and Prospects of Natural Glycoside Sweetener Biosynthesis: A Review

To achieve an adequate sense of sweetness with a healthy low-sugar diet, it is necessary to explore and produce sugar alternatives. Recently, glycoside sweeteners and their biosynthetic approaches have attracted the attention of researchers. In this review, we first outlined the synthetic pathways of glycoside sweeteners, including the key enzymes and rate-limiting steps. Next, we reviewed the progress in engineered microorganisms producing glycoside sweeteners, including de novo synthesis, whole-cell catalysis synthesis, and in vitro synthesis. The applications of metabolic engineering strategies, such as cofactor engineering and enzyme modification, in the optimization of glycoside sweetener biosynthesis were summarized. Finally, the prospects of combining enzyme engineering and machine learning strategies to enhance the production of glycoside sweeteners were discussed. This review provides a perspective on synthesizing glycoside sweeteners in microbial cells, theoretically guiding the bioproduction of glycoside sweeteners.

Applications of protein engineering in the microbial synthesis of plant triterpenoids

Triterpenoids are a class of natural products widely used in fields related to medicine and health due to their biological activities such as hepatoprotection, anti-inflammation, anti-viral, and anti-tumor. With the advancement in biotechnology, microorganisms have been used as cell factories to produce diverse natural products. Despite the significant progress that has been made in the construction of microbial cell factories for the heterogeneous biosynthesis of triterpenoids, the industrial production of triterpenoids employing microorganisms has been stymied due to the shortage of efficient enzymes as well as the low expression and low catalytic activity of heterologous proteins in microbes. Protein engineering has been demonstrated as an effective way for improving the specificity, catalytic activity, and stability of the enzyme, which can be employed to overcome these challenges. This review summarizes the current progress in the studies of Oxidosqualene cyclases (OSCs), cytochrome P450s (P450s), and UDP-glycosyltransferases (UGTs), the key enzymes in the triterpenoids synthetic pathway. The main obstacles restricting the efficient catalysis of these key enzymes are analyzed, the applications of protein engineering for the three key enzymes in the microbial synthesis of triterpenoids are systematically reviewed, and the challenges and prospects of protein engineering are also discussed.