Yongxian Fan

Cloning, expression and medium optimization of validamycin glycosyltransferase from Streptomyces hygroscopicus var. jinggangensis for the biotransformation of validoxylamine A to produce validamycin A using free resting cells

Validamycin A is widely used to control Basidiomycetes, which causes sheath blight disease in rice, potatoes, vegetables, and other crops as well as dumping-off disease in vegetable seedlings, cotton, sugar beets, and other plants. In order to improve the content of validamycin A in the commercial products, valG from Streptomyces hygroscopicus was successfully cloned into Escherichia coli BL21(DE3) and was directly employed as the biocatalyst in the biotransformation from validoxylamine A to validamycin A with the existence of d-cellobiose using the free resting cells in the present study. The fermentation medium was optimized through single factor experiment and response surface method. With the optimized medium, which contained lactose 4.7g/L, yeast extract 49.5g/L, ammonium chloride 2.7g/L, potassium phosphate buffer solution 110mL/L, Ca(2+) 0.0352g/L, the biomass yield and enzyme activity reached 5.5g/L and 1.49U/mL, respectively, which were nearly twice higher than those with initial medium.

Synthesis and antifungal evaluation of a series of maleimides

BACKGROUND Maleimides, both natural and synthesised, have good biological activities. In a continuous effort to discover new maleimides with good antifungal activities, the authors have synthesised a series of 3,4-dichloro-, 3-methyl and non-substituted maleimides based on previous studies. The compounds were biologically evaluated against the fungal pathogen Sclerotinia sclorotiorum. RESULTS Of the 63 compounds evaluated, 25 compounds had interesting inhibitory potency with EC50 < 10 µg mL(-1). N-(3,5-Dichlorophenyl)-3,4-dichloromaleimide (EC50 = 1.11 µg mL(-1)) and N-octyl-3-methylmaleimide (EC50 = 1.01 µg mL(-1)) were more potent than the commercial fungicide dicloran (EC50 = 1.72 µg mL(-1)). The results showed that compounds exhibiting log P values within the range 2.4-3.0 displayed the best results in terms of fungicidal activity, and this seemed, therefore, to be the optimum range for this physicochemical parameter. CONCLUSION The present work demonstrates that some maleimides can be used as potential lead compounds for developing novel antifungal agents against S. sclerotiorum.

Molecular cloning, expression of CPR gene from Rhizopus oryzae into Rhizopus nigericans and its application in the 11α-hydroxylation of 16α, 17-epoxy-progesterone.

The hydroxylations of the steroid skeleton structure are catalyzed by a family of enzymes, the cytochromes P450 (CYPs). In this study, the pCB1004-PgpdA plasmid was used for cloning the cytochrome P450 reductase (CPR) gene from Rhizopus oryzae into Rhizopus nigericans to strengthen the expression of CPR gene in R. nigericans with REMI (Restriction Enzyme Mediate Integration) mediated protoplast transformation. The conditions for the protoplast production of R. nigericans were optimized as follows: 75 μg/mL yatalase, 50 μg/mL lywallzyme, fungus age of 12h, digestion time of 3 h and digestion temperature of 30°C. REMI mediated protoplast transformation with plasmid pCB1004-PgpdA into R. nigericans was performed to construct the transformants. More than 30 transformants were successfully selected from the hygromycin B-resistant plates and 6 transformants had the abilities to improve the biotransformation of 16α, 17-epoxyprogesterone. The highest biotransformation rate of the transformants was 65.38%, which was 7.06% higher than that of the original strain.

Production of Validamycins

Validamycins have been used to efficiently prevent and treat sheath blight disease of corps including rice, wheat, potatoes, vegetables, strawberries, tobacco, ginger, and other crops. Thus it has large markets in China and eastern Asia with annual revenue of billions of Chinese dollars. In this chapter, the discovery of validamycins was first described. Then the microbes for producing validamycins were compared, including general characteristics and complete genomes. Later, production, isolation, structures, characterization and properties, biosynthesis, analysis, and microbial degradation of validamycins were presented. And gene engineering, including cloning, expression, and deficiency of genes in the biosynthesis, was reviewed, too. At last, fermentation process for production of validamycins in large scale was focused.

Chapter 7 – Prospects and Concluding Remarks

Validamycin has been one of most important agricultural antibiotics with a large market in China and other eastern Asian countries as a good plant protectant for decades. In this chapter, the market, prospects, and other important issues of validamycin are analyzed and expected.

Voglibose: An Important Drug for Type 2 Diabetes

Diabetes is one of the most important current diseases. Noninsulin-dependent diabetes mellitus (NIDDM), type 2 diabetes, is taking an increasing place both in developed and developing countries and is associated with a sedentary lifestyle and obesity. Voglibose is one of the important α-D-glucosidase inhibitors for treatment of NIDDM. In this chapter, the physico-chemical properties, preparation, pharmacology, pharmacokinetics, pharmacodynamics, clinical efficacy, safety, and tolerability of voglibose are reviewed in detail. Then in some aspects, voglibose is compared with acarbose and miglitol, another two important α-D-glucosidase inhibitors. Finally, the market and development of voglibose are analyzed and expected.

Chemical Synthesis of Validamycin and Related Natural Compounds

Because of their good biological activities, validamycins and their related natural compounds have attracted more and more researchers to synthesize them. Most of the research has focused on chemical synthesis of valienamine and valiolamine, important intermediates for voglibose, N -octyl-β-valienamine, and N -octyl-4- epi -β-valienamine. In addition, the total synthesis of validamycins and validoxylamines has been carried out by many research groups. Different kinds of chemicals, including glucose, L -quebranchitol, 2,3,4,6- tetra - O -benzyl- d -glucose, d -xylose, etc., have been employed as the starting materials.

Bioactivities of Validamycins and Related Natural Compounds

Abstract Validamycins and related natural compounds have good bioactivities, such as antifungal activities, enzymatic inhibitory activities, and insecticidal activities. Validamycins has good antifungal activity against Rhizoctonia Solani. The antifungal mechanism was complex. Validamycin A and validoxylamine A could also be used to control Fusarium wilt of tomato. As to other fungi, all the Basidiomycotina were sensitive to validamycin A. With the exception of Fusarium culmorum, Chaetomium globosum, and Chaetomium bostrychoides, all Ascomycotina, Oocyectes, and Mucorales tested were insensitive to validamycin A. Since the validoxylamines and validamycins are structurally similar to trehalose, they have good inhibitory activity for trehalase. Valienamine and related natural compounds has strong inhibitory activity for glucoside hydrolases. Most important of all, validoxylamine A has good insecticidal activity in vitro.

An Introduction to Validamycins and Their Derivatives

Abstract Validamycin is a magic agricultural antibiotic due to its outstanding merits such as excellent control effect, low price, low drug-resistance and low toxicity. Thus it has widely been used in Asia as the rice and wheat protectant against Rhizoctonia solani for decades. In this chapter, the simple introduction of antibiotics, agricultural antibiotics, and validamycins was described. Most of all, the aim of the book was provided in the context.

N -Octyl-β-Valienamine and N -Octyl-4- epi -β-Valienamine: Two Highly Potent Drug Candidates for Chemical Chaperone Therapy

Abstract Gaucher disease is a group of diverse clinical manifestations involving both the central nervous system and extraneural visceral organs, caused by β-glucosidase deficiency, resulting in massive storage of glucosylceramide. GM1-gagliosidosis is a relatively rare lysosomal disease caused by β-galactosidase deficiency. Both can be treated with chaperone therapy. N-Octyl-β-valienamine (NOV) and N-octyl-4-epi-β-valienamine (NOEV), are two highly potent drug candidates for chemical chaperone therapy for Gaucher disease and GM1-gagliosidosis, respectively. In this chapter, the preparation, physicochemical, and biological characteristics of NOV and NOEV are reviewed. Finally, future perspectives and conclusions for these two drugs are analyzed and drawn.