Chitosan is a biopolymer obtained from chitin, where the N-acetylglucosamine monomer is in its deacetylated form; this polymer is useful for a wide variety of industrial applications. The properties and uses of chitos...Chitosan is a biopolymer obtained from chitin, where the N-acetylglucosamine monomer is in its deacetylated form; this polymer is useful for a wide variety of industrial applications. The properties and uses of chitosan depend on its physical and chemical characteristics, which result from the treatments used for its production. In this study, we report the preparation and characterization ofchitosan oligosaccharides by a green synthesis from crystalline shrimp chitin, using a sequential enzyme treatment by chitinase and chitin deacetylase. Chitinases were purified from grapes and used to rupture the crystalline shrimp chitin structure, modifying the crystallinity index from 57.6% to 15.9%. The resultant polymers were deacetylated using a recombinant chitin deacetylase from Saccharomyces cerevisiae, which was cloned and expressed in Pichia pastoris. The chitosans produced showed an estimated DA （degree of acetylation） of approximately 20%, and the molecular weights ranged from -7,600 to -3,700 after treatment in pH 3.0 and pH 6.0 for 10 min and 40 min, respectively. Physical and chemical characterization of the products indicated that enzyme fragmentation of chitin probably makes the acetamide groups more accessible to deacetylation, forming homogeneous polymers that are free of hazardous sub-products, have defined low molecular weights, and are highly deacetylated.展开更多
Metabolism is a fundamental biological process composed of a series of reactions catalyzed by metabolic enzymes.Emerging evidence demonstrates that the aberrant signaling in cancer cells induces nonmetabolic functions...Metabolism is a fundamental biological process composed of a series of reactions catalyzed by metabolic enzymes.Emerging evidence demonstrates that the aberrant signaling in cancer cells induces nonmetabolic functions of meta-bolic enzymes in many instrumental cellular activities,which involve metabolic enzyme-mediated protein post-trans-lational modifications,such as phosphorylation,acetylation,and succinylation.In the most well-researched literatures,metabolic enzymes phosphorylate proteins rather than their metabolites as substrates.Some metabolic enzymes have altered subcellular localization,which allows their metabolic products to directly participate in nonmetabolic activities.This review discusses how these findings have deepened our understanding on enzymes originally classi-fied as metabolic enzymes,by highlighting the nonmetabolic functions of several metabolic enzymes responsible for the development of cancer,and evaluates the potential for targeting these functions in cancer treatment.展开更多
文摘Chitosan is a biopolymer obtained from chitin, where the N-acetylglucosamine monomer is in its deacetylated form; this polymer is useful for a wide variety of industrial applications. The properties and uses of chitosan depend on its physical and chemical characteristics, which result from the treatments used for its production. In this study, we report the preparation and characterization ofchitosan oligosaccharides by a green synthesis from crystalline shrimp chitin, using a sequential enzyme treatment by chitinase and chitin deacetylase. Chitinases were purified from grapes and used to rupture the crystalline shrimp chitin structure, modifying the crystallinity index from 57.6% to 15.9%. The resultant polymers were deacetylated using a recombinant chitin deacetylase from Saccharomyces cerevisiae, which was cloned and expressed in Pichia pastoris. The chitosans produced showed an estimated DA （degree of acetylation） of approximately 20%, and the molecular weights ranged from -7,600 to -3,700 after treatment in pH 3.0 and pH 6.0 for 10 min and 40 min, respectively. Physical and chemical characterization of the products indicated that enzyme fragmentation of chitin probably makes the acetamide groups more accessible to deacetylation, forming homogeneous polymers that are free of hazardous sub-products, have defined low molecular weights, and are highly deacetylated.
基金supported by the 2018 UT Proteomics Network Pilot Fund(to Y.W.)the NIH/NCI Cancer Center Support Grant P30CA016672Brain Cancer SPORE 2P50 CA127001。
文摘Metabolism is a fundamental biological process composed of a series of reactions catalyzed by metabolic enzymes.Emerging evidence demonstrates that the aberrant signaling in cancer cells induces nonmetabolic functions of meta-bolic enzymes in many instrumental cellular activities,which involve metabolic enzyme-mediated protein post-trans-lational modifications,such as phosphorylation,acetylation,and succinylation.In the most well-researched literatures,metabolic enzymes phosphorylate proteins rather than their metabolites as substrates.Some metabolic enzymes have altered subcellular localization,which allows their metabolic products to directly participate in nonmetabolic activities.This review discusses how these findings have deepened our understanding on enzymes originally classi-fied as metabolic enzymes,by highlighting the nonmetabolic functions of several metabolic enzymes responsible for the development of cancer,and evaluates the potential for targeting these functions in cancer treatment.
