酶解法提取纯化虎杖提取物中自藜芦醇的工艺研究

本文对虎杖提取物中虎杖苷的酶解条件及苷元白藜芦醇的提取纯化工艺进行研究,以样品中自藜芦醇的含量为指标,对纤维素酶、β-葡萄糖苷酶、复合酶进行筛选,结果表明以复合酶的水解效率最高:采用正交实验对影响复合酶酶解的因素:加酶量、温度、酶解时间进行考察;并对酶解后提取物中自藜芦醇的提取纯化工艺进行研究.得出如下较理想的酶解条件和提取纯化工艺:虎杖提取物,加水(pH 5)10倍,加20%的复合酶,于50℃保温24 h;酶解后的提取物经水、乙醇-水、碱溶液分步溶解沉淀,得白藜芦醇粗品,含量可达65%,工艺稳定可行.     

Estimation of lysine in compounded poultry diets after enzymic digestion

Lysine was estimated in compounded poultry diets after enzymic digestion at 41°C. Studies on growth were also conducted. Lysine contents of compounded starter rations when estimated after enzymic hydrolysis, conformed more accurately with the biological results than those obtained after acid hydrolysis.     

Various lipases for producing products enriched with polyenic acids in fish fat hydrolysis]

The enzymic hydrolysis of fish with lipases from various sources was studied. The lipase from the fungus Rhizopus microsporus preferentially removes saturated fatty acids, while lipase from the pyloric caeca of salmon unsaturated fatty acids upon hydrolysis of fish fats. The enzymes can be used to obtain fatty products enriched with eicosanopentaenoic acid, mono- and diacylglycerols by enzymic hydrolysis of the ivasi fat.     

A comparison of three methods of glycogen measurement in tissues

Three methods have been used for analysis of glycogen in tissue homogenates: hydrolysis of the tissue in acid and followed by enzymic analysis of the resulting glucose; enzymic hydrolysis with amylo-α-1,4-α-1,6-glucosidase, again followed by enzymic measurement of glucose; and degradation of the glycogen with phosphorylase and debrancher complex coupled to measurement of the resulting glucose-1-P. The two enzymic procedures yielded equivalent results with all tissues examined (brain, liver, muscle and polymorphonuclear leucocytes). Acid hydrolysis of the tissues resulted in higher values for brain tissue only, presumably due to the hydrolysis of the gangliosides and cerebrosides present in brain.     

Use of enzymic preparations during diosgenine isolation from Dioscorea caucasica Lipsky]

The use of enzymic preparations of the cellulolytic and macerating effect was studied as applied to the isolation of diosgenine from rhizomes of Dioscorea caucasica Lypsky. The enzymic treatment of the steroid containing raw material prior to acid hydrolysis increased the yield of diosgenine by 30-48%. It is suggested that additional extraction of diosgenine takes place due to: 1) enzymic hydrolysis of structural polysaccharide components of the plant tissue and intercellular binding materials and 2) disintegration of glycoside bonds of saponins.     

Boundaries of the butyrylcholinesterase anion site from data of a conformational analysis of substrates

By means of molecular mechanics, theoretical conformational analysis has been made of 19 substrates of butyrylcholinesterase - acetylcholine derivatives with different structure of the ammonium group. It was concluded that the anionic point is located in the cavity of the enzymic molecule. Dimensions and shape of this cavity were established which provide satisfactory correlation between its filling by substrate conformers and the rate of their enzymic hydrolysis. Some suggestions were made with respect to the mechanism of the effect of non-productive sorbtion of the substrates on the rate of their enzymic hydrolysis.     

Kinetics of enzymic hydrolysis of malto-oligosaccharides: A comparison with acid hydrolysis

The hydrolysis of malto-oligosaccharides G₃-G₆ catalysed by porcine pancreatic alpha-amylase was investigated kinetically at 25°. Kinetic parameters corresponding to different positions of enzymic attack were determined and product inhibition was evaluated. The enzymic hydrolysis was compared in terms of reaction rate and pattern of action with hydrolysis in 0.1m H₂SO₄ at 70°. Mathematical models for the mechanism of hydrolysis were developed and a good rationalisation of the experimental results was achieved.     

Complete enzymic digestion of acidic proteins.

Acidic proteins are usually resistant to complete enzymic hydrolysis. The increasing number of "unusual" amino acids, which are unstable to acid hydrolysis, makes it necessary to have a method of enzymic hydrolysis applicable to all proteins. The complete hydrolysis of four acidic proteins by subtilisin plus leucine amino-peptidase plus prolidase followed by carboxypeptidase C, is described. Recoveries of amino acids were in excellent agreement with the expected content from the known sequences.     

The study of hydrolysis of new lipid-like substrates and trilaurin in monolayers catalyzed with the lipase from Pseudomonas fluorescens

A simple method for determining the enzymic hydrolysis parameters of lipid-like substrates and trilaurin assembled in monolayers at the water-air interface was suggested. At a surface pressure of 10 mN/m, the initial rates of lipolysis were found to be proportional to the decrease in area of the substrate monolayer caused by the enzymic hydrolysis in a single-compartment Langmuir balance. The kinetic parameters for the hydrolysis of trilaurin and three 1,3-dilaurylpseudoglycerides acetylated in position 2 with an amino acid (phenylalanine, leucine, or valine) catalyzed with lipase from Pseudomonas fluorescens were determined. Unlike models of enzymic hydrolysis that neglect the thickness of the substrate monolayer, our method allows the determination of kinetic parameters in standard dimensions. The values of kcat for the synthetic pseudoglycerides were found to be significantly higher than that for trilaurin, while the values of Km(app) were close. This may be due to the presence of positively charged primary amino groups in the molecules of pseudoglycerides.     

The hydrolysis of new lipid-like substrates and trilaurin in monolayers catalyzed with the lipase fromPseudomonas fluorescens

A simple method for determining the enzymic hydrolysis parameters of lipid-like substrates and trilaurin assembled in monolayers at the water-air interface was suggested. At a surface pressure of 10 mN/m, the initial rates of lipolysis were found to be proportional to the decrease in area of the substrate monolayer caused by the enzymic hydrolysis in a single-compartment Langmuir balance. The kinetic parameters for the hydrolysis of trilaurin and three 1,3-dilaurylpseudoglycerides acetylated in position 2 with an amino acid (phenylalanine, leucine, or valine) catalyzed with lipase fromPseudomonas fluorescens were determined. Unlike models of enzymic hydrolysis that neglect the thickness of the substrate monolayer, our method allows the determination of kinetic parameters in standard dimensions. The values ofk _cat for the synthetic pseudoglycerides were found to be significantly higher than that for trilaurin, while the values ofK _m(app) were close. This may be due to the presence of positively charged primary amino groups in the molecules of pseudoglycerides.     

The enzymic hydrolysis of amygdalin

Chromatographic examination has shown that the enzymic hydrolysis of amygdalin by an almond beta-glucosidase preparation proceeds consecutively: amygdalin was hydrolysed to prunasin and glucose; prunasin to mandelonitrile and glucose; mandelonitrile to benzaldehyde and hydrocyanic acid. Gentiobiose was not formed during the enzymic hydrolysis. The kinetics of the production of mandelonitrile and hydrocyanic acid from amygdalin by the action of the beta-glucosidase preparation favour the probability that three different enzymes are involved, each specific for one hydrolytic stage, namely, amygdalin lyase, prunasin lyase and hydroxynitrile lyase. Cellulose acetate electrophoresis of the enzyme preparation showed that it contained a number of enzymically active components.     

土壤中选育产壳聚糖酶菌株的研究

采用酶法降解壳聚糖具有反应条件易于控制、产物安全性高和环境污染少等独特的优越性。因此,筛选出高活力产壳聚糖酶菌株有着重要意义。该研究以不同地区采集土样分离出的1株细菌为出发菌株S,采用紫外线诱变（30W,20cm,5min）,经初筛和复筛及控温培养处理,获得了一株产壳聚糖酶较好的突变菌株,结果表明：所产酶活力达到3．47U/ml,酶活力提高近2倍,并具有较好的遗传稳定性,明显优于出发菌株,为发酵产壳聚糖酶的进一步研究提供了高产菌株。     

Evidence for the presence of two separate protein activators for the enzymic hydrolysis of GM1 and GM2 gangliosides.

Two different protein activators were isolated simultaneously from human liver for the enzymic hydrolysis of GM1 (Gal beta 1 leads to 3GalNAc beta 1 leads to 4Gal(3 comes from 2 alpha NeuAc)beta 1 leads to 4Glc-Cer) by beta-galactosidase and GM2 (GalNAc beta 1 leads to 4Gal(3 comes from 2 alpha NeuAc)beta 1 leads to 4Glc-Cer) by beta-hexosaminidase A. The hydrolysis of GM1 is stimulated only by the GM1-specific activator which has very little effect on the hydrolysis of GM2. The same is also true for the hydrolysis of GM2. The antiserum raised against GM1 activator did not cross-react with GM2 activator and vice versa. These results suggest the presence of two different activators for the separate hydrolysis of GM1 and GM2. In connection with the enzymic hydrolysis of GM1 and GM2, we found that the hydrolysis of GM2 by human hepatic beta-N-acetylhexosaminidase A was severely inhibited by a buffer of high ionic strength, whereas no such inhibition was observed in the hydrolysis of GM1 by beta-galactosidase.     

The influence of glucose and ethanol on enzymic hydrolysis of steam-exploded bagasse

summary The rate of enzymic hydrolysis of steam-exploded bagasse was found to decrease linearly with increasing concentration of glucose and ethanol, with complete cessation of reaction predicted in the presence effects of glucose and ethanol were found to be additive. The significantly greater tolerance of the enzyme to ethanol can be utilised in the simultaneous hydrolysis and fermentation of bagasse cellulose to improve hydrolysis rate.     

Rapid and sensitive,colorimetric determination of the anomers of d-glucose with d-glucose oxidase,peroxidase, and mutarotase

A modification, utilising mutarotase, of an enzymic, colorimetric system for determining d-glucose with d-glucose oxidase, peroxidase, and ABTS was satisfactory for the assay of the anomers of d-glucose in aqueous solution. The time required for a single assay is ≈ 10 min, and the lower limit is 0.4 μg of d-glucose. The method is applicable to the anomer analysis of d-glucose released by enzymic hydrolysis of d-glucosides.     

Lability of equol to acidic hydrolysis procedures.

If equol is subjected to acidic hydrolysis by refluxing with 1.5 n HCl, a large proportion of the equol is altered to other substances. Subjection to enzymic hydrolysis by aryl sulfatase does not bring about any such alterations.     

Activation of human post heparin lipoprotein lipase by apolipoprotein H (β2-glycoprotein I)

Lipoprotein lipase (LPL) is the major enzyme involved in triglyceride hydrolysis of lymph chylomicrons and plasma very low density lipoproteins. LPL can be isolated from human post heparin plasma by heparin-Sepharose 4B affinity chromatography. In the present study the effects of apolipoproteins (apo) C-II, C-III, and H on the enzymic activity of LPL were investigated. ApoH is a recently described protein (β₂-glycoprotein I) constituent of triglyceride rich lipoproteins in human lymph and plasma. Human LPL was activated by apoC-II, and the apoC-II activation of LPL was inhibited by apoC-III. ApoH increased the enzymic activity of LPL in the presence of apoC-II by 45±17 percent. ApoC-III decreased the apoH + apoC-II enhanced activity of LPL by 77 percent. These results provide evidence for the concept that the enzymic activity of LPL in triglyceride metabolism is modulated by apoH. The relative proportion of apoH, apoC-II, and apoC-III in triglyceride rich lipoprotein particles may determine the ultimate rate of LPL catalyzed triglyceride hydrolysis.     

Hydrolysis of terpenyl glycosides in grape juice and other fruit juices: a review

The importance of monoterpenes on varietal flavour of must and other fruit juices has been reviewed. These compounds were mainly found linked to sugar moieties in grape juice and wines, showing no olfactory characteristics. In this way, analytical techniques developed to study these compounds, in both free or glycosidically forms, are discussed. Mechanisms to liberate terpenes were studied, making a comparative study between acidic and enzymic hydrolysis of terpene glycosides; as enzymic hydrolysis seems to be the most natural way to liberate terpenes, the ability to use glycosidases from grapes, yeasts, bacterial or exogenous, i.e. fungal commercial preparations, were reviewed. Re-arrangements of terpenes after acidic hydrolysis of glycoconjugated are discussed as well as potential adverse effects of enzyme preparations.     

The structure of a glycopeptide purified from porcine thyroglobulin

1. The structure of a purified glycopeptide isolated from porcine thyroglobulin was studied by sequential hydrolysis with specific glycosidases, by periodate oxidation and by treatment with galactose oxidase. 2. Sequential hydrolysis with several combinations of neuraminidase, alpha-l-fucosidase, beta-d-galactosidase, beta-N-acetyl-d-glucosaminidase and alpha-d-mannosidase presented the evidence for the following structure. 3. The monosaccharide sequence of the peripheral moiety of the heteropolysaccharide chain was sialic acid-->galactose-->N-acetylglucosamine. Some of the galactose residues were non-reducing end-groups with the sequence galactose-->N-acetylglucosamine. 4. After removal of the peripheral moiety composed of sialic acid, fucose, galactose and N-acetylglucosamine, alpha-mannosidase released 1.4mol of mannose/mol of glycopeptide, indicating that two of the three mannose residues were located between peripheral N-acetylglucosamine and internal N-acetylglucosamine or mannose. 5. Periodate oxidation and sodium borohydride reduction confirmed the results obtained by enzymic degradation and gave information concerning the position of substitution. 6. Based on the results obtained by enzymic hydrolysis and periodate oxidation together with the treatment with galactose oxidase, a structure is proposed for the glycopeptide.     

Castor-bean acid lipase catalysed hydrolysis of triacylglycerols does not involve C-2 → C-1,3 transacylation

The hydrolysis of a series of triacylglycerol analogs catalysed by castor-bean acid lipase was studied at 30° and pH 4.20. Iso-propyl esters underwent lipolysis, thus refuting the mechanistic proposition that hydrolysis at C-2 in triacylglycerols occurs via a slow transfer of the acyl moiety from C-2 to either C-1 or C-3, followed by enzymic hydrolytic action.