Anti-Alzheimer's Disease Effect of Polysaccharides from Zanthoxyli Pericarpium and Analysis of Its Structural Characteristics by Sugar Spectrum / 中国实验方剂学杂志

ObjectiveThe therapeutic effect of polysaccharides from Zanthoxyli Pericarpium on Alzheimer's disease（AD） was evaluated through establishing a mouse model of AD， and the structural characteristics of the polysaccharides was analyzed by sugar spectrum. MethodThe AD model of mice with rapid aging was established by intraperitoneal injection of D-galactose combined with gavage of aluminum trichloride， and the learning and memory ability of mice was evaluated by Morris water maze test， the histopathological status of brain and neuronal damage were observed by hematoxylin-eosin（HE） staining and Nissl staining. After hydrolysis of polysaccharides from Zanthoxyli Pericarpium with acid and different glycosidases， the characteristics of hydrolysates were analyzed by high performance thin layer chromatography（HPTLC） and fluorescence assisted carbohydrate gel electrophoresis（PACE）. HPTLC chromatography was performed on a silica gel 60 plate with sampling volume of 5 μL， developing solvent of ethyl acetate-glacial acetic acid-water（2∶2∶1）， developing twice， aniline-diphenylamine-phosphoric acid solution as chromogenic agent， and heating at 105 ℃ for 10 min， and then observed under sunlight. PACE experimental conditions were 34% separation gel and 8% concentration gel， electrophoresis buffer was 0.1 mol·L-1 tris（hydroxymethyl） aminomethane（Tris）-boric acid buffer（pH 8.2）. Electrophoresis was carried out at 0 ℃ and the loading amount was 3-6 μL. The sample ran to the front of the gel with a constant current of 15 mA， and imaged under ultraviolet 365 nm. ResultThe results of Morris water maze test showed that polysaccharides from Zanthoxyli Pericarpium significantly improved the learning and memory ability of AD model mice， shortened the escape latency， and significantly increased the number of crossing and the residence time in the target quadrant. The results of histopathological experiments showed that polysaccharides from Zanthoxyli Pericarpium could improve the pathological conditions and neuronal damage in the CA1 and CA3 regions of hippocampus of AD mice， and the number of Nissl corpuscles was significantly increased. The results of sugar spectrum analysis showed that the results of HPTLC and PACE analysis were basically consistent， polysaccharides from Zanthoxyli Pericarpium could be mainly hydrolyzed into small molecular sugars by cellulase and pectinase， indicating that they mainly contained β-1，4-glucosidic bond and α-1，4-galacturonic acid glycosidic bond， and could be slightly hydrolyzed by glucanase， β-galactosidase and β-mannase， indicating that they contained only a small amount of α-1，6-glucosidic bond， β-galactosidic bond， β-1，4-mannosidic bond. ConclusionPolysaccharides from Zanthoxyli Pericarpium has obvious therapeutic effect on AD mice， and its structure mainly contains β-1，4-glucosidic bond and α-1，4-galacturonic acid glycosidic bond， which can provide a reference for the structural analysis of traditional Chinese medicine polysaccharides.

Strategies for engineering the thermo-stability of glycosidase / 生物工程学报

Glycosidases are widely used in food and pharmaceutical industries due to its ability to hydrolyze the glycosidic bonds of various sugar-containing compounds including glycosides, oligosaccharides and polysaccharides to generate derivatives with important physiological and pharmacological activity. While glycosidases often need to be used under high temperature to improve reaction efficiency and reduce contamination, most glycosidases are mesophilic enzymes with low activity under industrial production conditions. It is therefore critical to improve the thermo-stability of glycosidases. This review summarizes the recent advances achieved in engineering the thermo-stability of glycosidases using strategies such as directed evolution, rational design and semi-rational design. We also compared the pros and cons of various techniques and discussed the future prospects in this area.

Application of immobilized glycosidase in the synthesis of glycoside compounds / 生物工程学报

Glycoside compounds are widely used in medicine, food, surfactant, and cosmetics. The glycosidase-catalyzed synthesis of glycoside can be operated at mild reaction conditions with low material cost. The glycosidase-catalyzed processes include reverse hydrolysis and transglycosylation, appropriately reducing the water activity in both processes may effectively improve the catalytic efficiency of glucosidase. However, glucosidase is prone to be deactivated at low water activity. Thus, glucosidase was immobilized to maintain its activity in the low water activity environment, and even in neat organic solvent system. This article summarizes the advances in glycosidase immobilization in the past 30 years, including single or comprehensive immobilization techniques, and immobilization techniques combined with genetic engineering, with the aim to provide a reference for the synthesis of glycosides using immobilized glycosidases.

Bioactivity and Chemical Constituents of Different Polar Parts from Blueberry Leaves / 中国药学杂志

OBJECTIVE: To study the bioactivity and chemical constituents of different polar parts from blueberry leaves. METHODS: Blueberry leaves were extracted by ethanol and then the extract was sequentially partitioned into five fractions. Silicagel and Sephadex LH-20 chromatographic methods were applied to isolate and purify compounds. Their structures were elucidated by physiochemical properties and spectral analysis.The DPPH• radical scavenging activity, α-glycosidase and pancreatic lipase inhibition activity of different polar parts and partial compounds were determined. RESULTS: The n-butyl alcohol fraction(BF) showed the highest DPPH• radical scavenging activity and α-glycosidase inhibition activity. The ethyl acetate fraction(EAF) showed the strongest pancreatic lipase inhibition activity. A total of five compounds were isolated from the EAF, and their structures were identified as β-sitosterol(1), quercetin-3-O-α-L-arabinofuranoside(2), quercetin(3), quercetin-3-O-β-D-glucopyranoside(4) and 1-O-caffeoylquinic acid(5). A total of two compounds were isolated from the BF, and their structures were identified as quercetin-3-O-α-L-arabinoside(6) and quercetin-3-O-β-D-glucuronide(7). The results showed that compounds 3 and 5 had very good DPPH• radical scavenging and pancreatic lipase inhibitory activity, and compounds 1 and 3 had good α-glucosidase inhibitory activity. CONCLUSION: The different polar parts and compounds of blueberry leaves show strong DPPH• radical scavenging activity, α-glycosidase and pancreatic lipase inhibition activity. Compounds 1, 2, 5 and 6 are isolated from blueberry leaves for the first time.

Enzymatic synthesis of mogroside ⅢE / 中国药科大学学报

The aim was to develop the simple preparation method of mogroside ⅢE,and to lay the foundation for the development of the mogroside sweeteners. In the present study,the glycosidase CPU-GH17,which can regio-selectively biosynthesize mogroside ⅢE from mogroside V,was screened from the established library of glycosi-dases. Then,the soluble expression condition of CPU-GH17 in E. coli was exploited by investigating isopropyl β-D-thiogalactoside (IPTG)concentration,culture temperature and induction time,and 0. 4 mmol/L IPTG,15 °C and 12 h was used as optimal condition. The result showed that mogroside V could be completely converted into mogroside ⅢE under the conditions of pH 6. 0,45 °C,3 U/mL enzyme loading,5 mg/mL substrate concentration for 20 h. In conclusion,a biosynthetic system for the regio-selective preparation of mogroside ⅢE by recombinant CPU-GH17 was successfully established and verified at a preparative scale.

Aqueous extract of Psidium guajava leaves: phenolic compounds and inhibitory potential on digestive enzymes

ABSTRACT Leaves of Psidium guajava L. (guava) have been widely used in the popular way for prevention and treatment of various diseases. Thus, the objective of this study was to evaluate the inhibitory potential of leaves aqueous extract from three cultivars of P. guajava (Pedro Sato, Paluma and Século XXI) on α-amylase, α-glycosidase, lipase, and trypsin enzymes, in the presence or not of simulated gastric fluid and to determine the content of phenolic compounds by high performance liquid chromatography. All cultivars presented the same composition in phenolic compounds, but in different proportions. The compounds identified are gallic acid, epigallocatechin gallate, syringic acid, o-coumaric acid, resveratrol, quercetin, and catechin (which was the major compound in all the cultivars evaluated). In the absence of simulated gastric fluid, it was observed different inhibitions exercised by the leaves aqueous extracts from three cultivars of P. guajava on each enzyme. In presence of simulated gastric fluid, all cultivars showed increase in the inhibition of lipase and α-glycosidase, and decrease in inhibition of α-amylase and trypsin enzymes. These results indicate that P. guajava leaves aqueous extracts from all cultivars evaluated possess potential of use as an adjuvant in the treatment of obesity and other dyslipidemias.

Research progress on treatment of diabetes with Tibetan medicine Huidouba / 中草药

Diabetes is a metabolic disorder characterized by insulin resistance and progressive failure of β cell. It becomes a major disease and causes much attention because of high incidence, high disability, and high morbidity. Traditional Chinese medicine and ethical minority medicine have certain effects on diabetes, such as regulating lipid and losing weight, improving insulin resistance, and reducing hypoglycemia risk, and also have obvious advantage in therapy for vascular complication. Studies show that Tibetan Huidouba can improve metabolism of blood glucose, triglyceride (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), activity of superoxide dismutase (SOD) and malondialdehyde (MDA) content in diabetic animal. The metabolism includes inhibiting α-glycosidase enzyme, activating peroxisome proliferators activated receptors (PPAR), and inhibiting nicotinamide adenine dinucleotide phosphate coenzyme II (NADPH) oxidase.

Study on in vitro hypoglycemic effect and mechanism of Polygonum capitatum / 中草药

Objective: To investigate the hypoglycemic targets of Polygonum capitatum. Methods: Human liver cancer HepG2 cells were adopted to detect the supernatant culture medium glucose content, and the effect on PPAR-α and GLUT4 gene expression was investigated by qRT-PCR after treatment of P. capitatum extracts (PCB). INS-1 cells similar to islet β cells, divided into drug protection group and repair group, were adopted to determine the cell proliferation activity by MTT; The intracellular SOD and MDA levels were measured by biochemical method; The Cyt C and Caspase-3 protein expression levels were detected by Western blotting. Adopting maltose as substrate of α-glycosidase enzyme inhibition model, the inhibitory efficiency of PCB on glycosidic enzyme was determined. Results: PCB group significantly promoted the absorption of HepG2 cells to supernatant glucose and increased the expression of PPAR-α and GLUT4 genes significantly. Aim at protection and repair of INS-1 cells, PCB group significantly increased cell vitality and SOD level, reduced MDA level compared with model group, and at the same time significantly reduced Cyt C and Caspase-3 protein expression levels. PCB had inhibitory activity to α-glycosidase enzymes, with IC50 of 11.53 mg/mL. Conclusion: PCB could significantly increase the PPAR-α and GLUT4 genes expression to promote the absorption of HepG2 cells to supernatant glucose by blocking the Cyt C-Caspase-3 pathways to reduce apoptosis of islet cells which were damaged by STZ and by raising SOD and declining MDA to improve INS-1 cell oxidative stress; What’s more it has inhibitory activity to α-glycosidase enzymes.

Virtual Screening ofα-glycosidase Inhibitors in Cortex mori and Folium mori / 中国药房

OBJECTIVE:To virtually screen potential α-glycosidase inhibitor ingredients from C. mori and F. mori,and to pro-vide reference for finding out new typeα-glycosidase inhibitor ingredient. METHODS:Surflex-Dock module of Sybyl-x 2.0 molecu-lar simulation software was used to perform the docking of small molecule compound,which was from the ingredients of C. mori and F. mori as ligand stated in literatures,with α-glycosidase. Total score of affinity scoring function was equal to 7 as the thresh-old value,to judge potential α-glycosidase inhibitor ingredient in C. mori and F. mori. RESULTS:After 70 small molecule com-pounds docked with α-glycosidase, 10 compounds showed binding activity (Total score≥7.00). Among them, moracin M-3′-O-β-D-glucopyranoside,5,7,2′-trihydroxyflavanone-4′-O-β-D-glucoside,mulberroside A,resveratrol-4,3′-di-O-β-D-gluco-pyranoside and 1,4-dideoxy-1,4-imino-(2-O-β-D-glucopyranosyl)-D-arabinitol had higher binding activity with α-glycosidase(Total score>8.00). CONCLUSIONS:Multi-constituents of C. mori and F. Mori show potential α-glycosidase inhibitory activity. The method is a kind of highly targeted,rapid and efficient approach to discover α-glycosidase inhibitor from traditional Chinese medi-cine.

Diagnostic value of urine RBP,NAG combined with serum CysC detection in early kidney damage in type 2 diabetes mellitus / 国际检验医学杂志

Objective To explore the diagnostic value of urine retinol binding protein (RBP) ,beta‐N‐acetyl amino glycosidase enzymes(NAG) combined with serum cystatin C (CysC) detection in early kidney damage of type 2 diabetes mellitus (T2DM ) . Methods Totally 58 cases of T2DM complicating in our hospital were selected as the group A ,54 cases of simple T2DM (group B) and 52 individuals undergoing the physical examination(group C) .The urine RBP ,NAG and serum CysC were detected in three groups ,their differences were compared .The positive rates for detecting early diabetic renal damage were compared between the single index detection and combined detection .Results The levels of urine RBP ,NAG and serum CysC level in the group A were significantly higher than those in the group B and C ,the differences were statistically significant (P< 0 .05);the levels of urine RBP ,NAG and serum CysC level in the group B were significantly higher than those in the group C ,the differences were statistical‐ly significant(P<0 .05);The positive rates of single detection of RBP ,NAG and CysC were 87 .93% ,86 .21% and 84 .48% respec‐tively ,the positive rate of 3‐index combined detection was 94 .83% ,which was significantly higher than that of single index detec‐tion ,the difference was statistically significant (P<0 .05) .Conclusion Urine RBP ,NAG and serum CysC are the sensitive indexes in early diabetic renal damage .The 3‐index combined detection has better comprehensive sensitivity and possesses higher clinical ap‐plication value .

Evaluation of standardisation parameters, pharmacognostic study, preliminary phytochemical screening and in vitro antidiabetic activity of Coccinia indica fruits as per WHO guidelines.

Coccinia indica an annual creeper is available all over India and well known for its antidiabetic property. In the present investigation, aqueous extract, and ethanolic extract of the fruits were made using hot extraction procedure using soxhlet apparatus, decoction and maceration. The qualitative phyto-chemical screening procedure was performed on each extract. Phyto-chemical study reveals that carbohydrates, tannins, phenols, alkaloids, saponins was present in both the extracts. An attempt has been made to highlight this folk herbal medicine through present study which will assist in the identification of fresh as well as dried crude samples of fruits anatomically and physiochemically. TLC finger printing and fluorescence analysis of powdered fruits has been conducted and reported .The antidiabetic activity is conducted by enzyme inhibition (α-glycosidase) in invitro method on each extract and ethanolic extract showed significant inhibition.

Streptozotocin-induced diabetes mellitus affects lysosomal enzymes in rat liver

It has been previously shown that dextran sulfate administered to diabetic rats accumulates in the liver and kidney, and this could be due to a malfunction of the lysosomal digestive pathway. The aim of the present study was to evaluate the expression and activities of lysosomal enzymes that act upon proteins and sulfated polysaccharides in the livers of diabetic rats. Diabetes mellitus was induced by streptozotocin in 26 male Wistar rats (12 weeks old), while 26 age-matched controls received only vehicle. The livers were removed on either the 10th or the 30th day of the disease, weighed, and used to evaluate the activity, expression, and localization of lysosomal enzymes. A 50-60% decrease in the specific activities of cysteine proteases, especially cathepsin B, was observed in streptozotocin-induced diabetes mellitus. Expression (mRNA) of cathepsins B and L was also decreased on the 10th, but not on the 30th day. Sulfatase decreased 30% on the 30th day, while glycosidases did not vary (or presented a transitory and slight decrease). There were no apparent changes in liver morphology, and immunohistochemistry revealed the presence of cathepsin B in hepatocyte granules. The decrease in sulfatase could be responsible for the dextran sulfate build-up in the diabetic liver, since the action of sulfatase precedes glycosidases in the digestive pathway of sulfated polysaccharides. Our findings suggest that the decreased activities of cathepsins resulted from decreased expression of their genes, and not from general lysosomal failure, because the levels of glycosidases were normal in the diabetic liver.

Analysis of relationship between protein expression of XRCC3 and HOGG1 and prognosis in patients with esophageal squamous cell carcinoma after radiotherapy / 中华放射肿瘤学杂志

Objective To investigate the relationship between the protein expression of X-ray repair cross-complementing protein 3 (XRCC3) and human 8-hydroxyguanine glycosylase 1 (HOGG1) in esophageal squamous cell carcinoma (ESCC) tissue and the prognosis in ESCC patients after radiotherapy.Methods Immunohistochemical SP method was used to measure the protein expression of XRCC3 and HOGG1 in 171 ESCC tissue samples before radiotherapy.The Kaplan-Meier method was used for survival analysis,and the logrank test was used for analyzing the survival difference between negative and positive samples.The Cox model was used for multivariate prognostic analysis.Results The follow-up rate was 87.2％ ; 140 patients were followed up for at least 1 year,136 patients for at least 2 years,and 129 patients for at least 3 years.XRCC3 was mainly expressed in the nucleus,and HOGG1 was mainly expressed in the nucleus and mitochondria,with a coincidence degree of 72.5％ (x2 =23.94,P =0.000).The patients with positive XRCC3 expression and negative XRCC3 expression had similar short-term responses (x2 =0.98,P =0.614)as well as similar survival rates,and both patient groups had a median survival time of 54 months (x2 =0.17,P =0.683).The patients with positive HOGG1 expression and negative HOGG1 expression had similar short-term responses (x2 =0.26,P =0.880) as well as similar survival rates,and both patient groups had a median survival time of 49 months (x2 =0.08,P =0.780).The multivariate prognostic analysis showed that the response evaluation and tumor length were related to the prognosis of ESCC (x2 =7.99,P =0.005 ; x2 =3.76,P =0.045).Conclusions The protein expression of XRCC3 and HOGG1 may be unrelated to the prognosis of ESCC after radiotherapy.

Hydrolytic potential of a psychrotrophic Pseudomonas isolated from refrigerated raw milk

The production of extracellular hydrolases by a psychrotrophic bacterium isolated from refrigerated raw milk, and identified as a Pseudomonas sp. belonging to the Pseudomonas jenssenii group, was studied. This bacterium produced proteolytic and lipolytic enzymes in all media investigated (skim milk, cheese whey, casein broth, and tryptone soy broth). High levels of á-glucosidase were produced in skim milk broth. Hydrolytic enzymes detected in skim milk broth are of particular concern, indicating that these enzymes could be produced by Pseudomonas sp. during the cold storage of raw milk, contributing to the spoilage problem in milk and dairy products.

Characterization of the interdependency between residues that bind the substrate in a â-glycosidase

The manner by which effects of simultaneous mutations combine to change enzymatic activity is not easily predictable because these effects are not always additive in a linear manner. Hence, the characterization of the effects of simultaneous mutations of amino acid residues that bind the substrate can make a significant contribution to the understanding of the substrate specificity of enzymes. In the â-glycosidase from Spodoptera frugiperda (Sfâgly), both residues Q39 and E451 interact with the substrate and this is essential for defining substrate specificity. Double mutants of Sfâgly (A451E39, S451E39 and S451N39) were prepared by site-directed mutagenesis, expressed in bacteria and purified using affinity chromatography. These enzymes were characterized using p-nitrophenyl â-galactoside and p-nitrophenyl â-fucoside as substrates. The k cat/Km ratio for single and double mutants of Sfâgly containing site-directed mutations at positions Q39 and E451 was used to demonstrate that the effect on the free energy of ES‡ (enzyme-transition state complex) of the double mutations (∆∆G‡xy) is not the sum of the effects resulting from the single mutations (∆∆G‡x and ∆∆G‡y). This difference in ∆∆G‡ indicates that the effects of the single mutations partially overlap. Hence, this common effect counts only once in ∆∆G‡xy. Crystallographic data on â-glycosidases reveal the presence of a bidentate hydrogen bond involving residues Q39 and E451 and the same hydroxyl group of the substrate. Therefore, both thermodynamic and crystallographic data suggest that residues Q39 and E451 exert a mutual influence on their respective interactions with the substrate.

Union examination of AFP, AFU, AFPL3 andγ-GT in early diagnosis of primary liver cancer / 药物分析学报

Objective To explore the significance of union examination of blood serum liver cancer tracers in the early diagnosis of liver cancer. Methods We observed and compared the level of blood serum liver cancer tracers armor embryo protein (AFP), crag algae glycosidase (AFU), armor embryo protein heteroplasmon (AFPL3) andγ-Gu Anxian transferase (γ-GT) in early time for primary liver cancer patients and hepatitis liver cirrhosis patients and those chronic hepatitis B patients who had liver cancer family history. Results Finally among the 30 patients in the early liver cancer group, 23 were positive with AFP, 20 with AFU, 15 with AFPL3 and 21 with γ-GT. Five were found positive with blood serum AFP, AFPL3, AFU and γ-GT at the same time; 5 with AFP, AFPL3 and γ-GT; 5 with AFP, AFU and AFPL3; 7 with AFP, AFU andγ-GT. By contrast, in the control group, among the 30 hepatitis liver cirrhosis patients and those chronic hepatitis B patients with liver cancer family history, 11 were found positive with AFP, 3 with AFPL3, 12 with AFU and 14 with γ-GT. None of the patients were found positive with union examination of AFP, AFPL3, AFU and γ-GT in the blood serum at the same time. Conclusion The union examination of AFP, AFU, AFPL3 and γ-GT is significant to the early diagnosis of primary liver cancer.

Union examination of AFP, AFU, AFPL3 and γ-GT in early diagnosis of primary liver cancer / 西安交通大学学报·英文版

Objective: To explore the significance of union examination of blood serum liver cancer tracers in the early diagnosis of liver cancer. Methods: We observed and compared the level of blood serum liver cancer tracers armor embryo protein (AFP), crag algae glycosidase (AFU), armor embryo protein heteroplasmon (AFPL3) and γ-Gu Anxian transferase (γ-GT) in early time for primary liver cancer patients and hepatitis liver cirrhosis patients and those chronic hepatitis B patients who had liver cancer family history. Results: Finally among the 30 patients in the early liver cancer group, 23 were positive with AFP, 20 with AFU, 15 with AFPL3 and 21 with γ-GT. Five were found positive with blood serum AFP, AFPL3, AFU and γ-GT at the same time; 5 with AFP, AFPL3 and γ-GT, 5 with AFP, AFU and AFPL3; 7 with AFP, AFU and γ-GT. By contrast, in the control group, among the 30 hepatitis liver cirrhosis patients and those chronic hepatitis B patients with liver cancer family history, 11 were found positive with AFP, 3 with AFPL3, 12 with AFU and 14 with γ-GT. None of the patients were found positive with union examination of AFP, AFPL3, AFU and γ-GT in the blood serum at the same time. Conclusion: The union examination of AFP, AFU, AFPL3 and γ-GT is significant to the early diagnosis of primary liver cancer.

Synthesis of a salacinol analogue and its α-glucosidase inhibitory activity / 药学学报

Aim To investigate more efficient synthetic method of the nitrogen analogue 4 of salacinol (1) for searching new antidiabetic agents. Methods The synthesis of the key intermediate 2,4-O-isopropylidene-L-erythritol 1,3-cyclic sulfate (2a) was accomplished by modification of reports from Dglucose via seven steps in much more less expensive. Using this method, an efficient synthesis of 4 was carried out. The glycosidase inhibitory activity of 4 was tested for the intestinal α-glucosidase in vitro and compared with that of salacinol. Results A nitrogen analogue 4 of salacinol (1) was synthesized by the coupling reaction between the cyclic sulfate 2a and an azasugar 3b. Conclusion Substitution of the sulfur atom in 1 with a nitrogen reduced the activity considerably.

Effects of acarbose on the expression of obese and neuropeptide Y (NPY) genes in mice on high-carbohydrate diet

Two components of the neuroendocrine-hormonal response to long-term treatment of acarbose, adipose tissue-derived leptin and central neuropeptide Y (NPY), were investigated in the ICR mice on a high-carbohydrate diet. Acarbose, administered 5 or 50 mg per 100 g diet for four weeks, dose dependently suppressed body weight gain. The body weight gain was reduced along with the amount of daily food intake in 50 mg acarbose-treated group at 7th and 28th day 5 or 50 mg acarbose treatment administered for four weeks reduced leptin mRNA levels to 62% and 77% of the control group, demonstrating that the amount of leptin mRNA in adipocytes correlates with body weight. As dose of acarbose increased, leptin mRNA level also increased, suggesting that potent inhibition of alpha-glycosidase by a higher dose of acarbose furthers the enzyme activity and leptin gene consequently. On the other hand, central expression level of NPY gene was increased significantly compared with the control group at the same amount of acarbose administered, reflecting that leptin and NPY operate in a negative-feedback circuit to regulate body fat stores.

THE CHEMICAL COMPOSITION AND SPECTRUM CHARACTERISTICS OF GLUCOAMYLASE FROM AN ASPERGILLUS NIGER MUTANT / 微生物学通报

Purified GAI, one form of glucoamylase obtained from Aspergillus niger mutant T21 contained 17.6% total carbohydrate. Analyses of amino acid composition showed that GAI contained about 25% Ser and Thr, 20.3% Asx and Glx and 6% basic amino acids. The UV absorption and fluorescence spectra of GAI were determined. The maximum absorption wavelength was at 278nm and minimum at 250nm. For fluorescent analyses the excitation and maximum emission spectra were at 284nm and 342nm respectively. The CD-spectrum determined showed two negative peaks. Its dispersion of secondary structure in solution showed 10.6% ?-helix, 16.3% ?-form and 73.1% unordered.