环腺苷酸和某些酶系合成的降解物阻遏之关系

用巨大芽孢杆菌(Bacillus megaterium AS 1.217)和两株大肠杆菌(Escherickia coli AS 1.797和E.coli K12)研究了环腺苷酸(CAMP)与乳糖和半乳糖利用的降解物阻遏的关系。结果显示,自身不合CAMP的巨大芽孢杆菌在葡萄糖和乳糖混合碳源中培养时,利用乳糖的酶系之合成受葡萄糖的阻遏与CAMP无关;E.coli AS 1.797在同样的混合碳源中培养时,葡萄糖的阻遏作用可用外源CAMP消除,这说明,在这种细菌内,利用乳糖的酶系之合成依赖于CAMP。葡萄糖对半乳糖利用的阻遏与CAMP的关系因不同菌株而异:对于E.coli K12,外源CAMP能消除葡萄糖的阻遏作用;对于E.coli AS 1.797,同样浓度的外源CAMP则不能消除葡萄糖的阻遏作用,但能减轻这种阻遏作用。这似乎表明,在E.coli AS 1.797内,利用半乳糖的酶系之合成对CAMP浓度的要求可能不同于E.coli K12的这一要求。

双歧杆菌的代谢及开发前景

双歧杆菌(Bifidobacterium)是典型的益生菌,与机体的许多生理、病理现象关系密切,引起生物学、医学、免疫学、营养学、遗传学、食品学等领域的专家学者的广泛关注。综述了双歧杆菌的生物学特性、厌氧机理、有关酶系合成、分泌到菌体外的物质、质粒研究及双歧杆菌制品的开发利用。

Toward modular construction of cell‐free multienzyme systems

The implementation of multiple enzymes for chemical production in a cell‐free scenario is an emerging field in biomanufacturing.It enables the redesign and reconstitution of new enzymatic routes for producing chemicals that may be hard to obtain from natural pathways.Although the construction of a cell‐free multienzyme system is highly flexible and adaptable,it is challenging to make all enzymatic reactions act in concert.Recently,modular construction has been conceptual‐ized as an effective way to harmonize diverse enzymatic reactions.In this review,we introduce the concept of a multienzyme module and exemplify representative modules found in Nature.We then categorize recent developments of synthetic multienzyme modules into main‐reaction modules and auxiliary modules according to their roles in reaction routes.We highlight four main‐reaction mod‐ules that can perform carbon metabolism,carbon assimilation,protein glycosylation and nonribo‐somal peptide synthesis,and exemplify auxiliary modules used for energy supply,protection and reinforcement for main reactions.The reactor‐level modularization of multienzyme catalysis is also discussed.

Green Synthesis and Physical and Chemical Characterization of Chitosans with a High Degree of Deacetylation, Produced by a Binary Enzyme System

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.

Chemomics and drug innovation

Chemomics is an interdisciplinary study using approaches from chemoinformatics,bioinformatics,synthetic chemistry,and other related disciplines.Biological systems make natural products from endogenous small molecules (natural product building blocks) through a sequence of enzyme catalytic reactions.For each reaction,the natural product building blocks may contribute a group of atoms to the target natural product.We describe this group of atoms as a chemoyl.A chemome is the complete set of chemoyls in an organism.Chemomics studies chemomes and the principles of natural product syntheses and evolutions.Driven by survival and reproductive demands,biological systems have developed effective protocols to synthesize natural products in order to respond to environmental changes;this results in biological and chemical diversity.In recent years,it has been realized that one of the bottlenecks in drug discovery is the lack of chemical resources for drug screening.Chemomics may solve this problem by revealing the rules governing the creation of chemical diversity in biological systems,and by developing biomimetic synthesis approaches to make quasi natural product libraries for drug screening.This treatise introduces chemomics and outlines its contents and potential applications in the fields of drug innovation.