摘要:

ABSTRACTAn α‐amylase inhibitor from rye (Secale cereale) flour has been purified to homogeneity by extraction with 70% ethanol, ammonium sulfate fractionation and column chromatography on DEAE‐ and CM‐cellulose. The isoelectric point was pH 5.8, and the molecular weight 28,000 by polyacrylamide gel electrophoresis with different gel concentrations and 27,000 by sedimentation equilibrium centrifugation. Under denaturating conditions the molecular weight was about 14,000, indicating two subunits identical in size. The inhibitor was active towards human salivary and hog pancreatic α‐amylases but inactive towards Bacillus subtilis and Aspergillus oryzae α‐amylases. The pH optimum for the reaction between the rye inhibitor and human salivary α‐amylase was 6.0. The inhibitor did not change activity when exposed to pH 2 (0.01M HCl), but prolonged digestion by trypsin destroyed the inhibitor. The rye α‐amylase inhibitor lost about 80% of its activity aft

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00607.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTRaw albacore tuna was separated into water‐soluble and water‐insoluble fractions. The water‐soluble fraction was separated into two fractions by trichloroacetic acid (2.5%). The water‐insoluble fraction was extracted with NaCl (0.45 M), and then the insoluble fraction was further extracted with urea solution (6 M). H2S production upon heating of each fraction was determined by the reflux‐trap technique. Water‐soluble proteins produced 71% of the H2S, while the corresponding contribution from the insoluble fraction was 29%. Non‐protein soluble components and salt‐soluble proteins produced insignificant amounts of H2S. Significant increase in the amount of H2S was observed when water‐insoluble proteins were treated with urea

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00608.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTZahdi dates (Phoenix dactylifera) contain invertase at all development stages; the highest specific activity is present in the late yellow stage. The enzyme was purified to homogeneity, as determined by disc gel electrophoresis and isoelectric focusing, by a combination of techniques including ammonium sulfate precipitation, DEAE‐cellulose chromatography and gel filtration on Sepharose 4B and Sephadex G‐150 columns. A complex of invertase with a high molecular weight pectic substance of the date could not be dissociated by ammonium sulfate or DEAE‐cellulose chromatography but the complex was dissociated by gel filtration on a Sepharose 4B column at pH 4.0 and ionic strength of 0.5 M. The enzyme contained 8.2% carbohydrate covalently linked probably via an amide linkage to aspartic acid. Molecular weight determination by exclusion gel chromatography and sedimentation equilibrium gave values of 130,000 and 97,100 ± 1,300, respectively. The enzyme is probably composed of two identical subunits as shown by SDS polyacrylamide gel electrophoresis. Amino acid analyses showed the enzyme to be low in sulfur‐containing amino acids. Date invertase is an acid β‐fructofuranosidase with a pH optimum between 3–4 and with a Kmand kcatfor sucrose of 6mM and 49 sec‐1,respectively. Activation energies for denaturation of enzyme and conversion of substrate to product were determined to be 48.7 and 17.6 kcal/mole, respectively. Chemical modification indicated that sulfhydryl groups are probably not essential for activity while carboxyl groups may be involved in the active sit

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00609.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTSoluble peroxidase activity extracted from purple, green and white eggplants (Solanum melongena L.) was measured spectrophotometrically. Activity was significantly higher in the white variety than in the other two. The isozyme patterns were compared by polyacrylamide gel electrophoresis. The purple and green had 3 major isozyme bands between 0.8 and 0.9 Rf while the white contained 2. Only the white and purple cultivars contained bands between 0.06 and 0.3 and 0.6 and 0.7 Rf.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00610.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTThe plasma membrane of Saccharomyces carlsbergensis was isolated by lysis of protoplasts and purified by ultracentrifugation in a discontinuous sucrose gradient. Extraction of the purified membranes with buffer in the absence of Mg2+ released 80% of the membrane protein as macromolecular complexes. Solubilization of the membranes in sodium dodecyl sulfate (SDS) caused the majority of the membrane protein to be dissociated from the membrane phospholipid, but after gel filtration some material appeared consistently as an SDS‐stable lipo‐protein, which aggregated to visible particles if the solubilizing detergent was removed, was not associated with Mg2+‐ATPase. Calcium appeared to be involved in the linkage of membrane phospholipid to protein while the reaction of magnesium was at the protein‐protein level. Calcium had high affinity of binding to the membrane proteins compared to magnesium ions. Potassium was loosely associated with all membrane proteins. On separation of the membranes by SDS‐polyacrylamide gel electrophoresis, 19 polypeptides were distinguished, with molecular weights from 185,000 to 14,000. At least 2 polypeptides with molecular weights of 17,000 and 14,000 were involved in the binding of divalent ions by the

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00611.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTInvestigation of the effects of selected enzymatic pretreatments of alfalfa leaves on plant protein recovery by mechanical expression of cell contents showed significantly higher crude protein recoveries for enzymatically treated extracts as compared with untreated samples. Protein recovery increases were seen for leaves pretreated with a buffered cellulase and a cellulase‐pectinase mixture. However, protein recoveries were not increased by pretreatment with a pectinase or a phospholipase. The increases were partly due to nonspecific buffer effects associated with leaching or osmotic shock and were pH dependent. The increases were also partly due to specific enzymatic effects which appear to result from structural degradation of plant tissue, as seen in electron micrographs, leading to enhanced cell rupture and release of cytoplasmic materials. The effect of enzymatic pretreatment is thought to result in accelerated senescence by degrading major structural components which provide rigidity and mechanical strength in plant tissue. This may be primarily related to the degradation of structural polysaccharides of the cell wall and middle lamell

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00612.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Book Reviews in this Article:Cellular Energy Metabolism and Its Regulation.Daniel F. Atkinson.The Tools of Biochemistry.Terrance G . Cooper.Cryochemistry ‐ An Introduction.Pierre Douzou.Membranous Elements and Movement of Molecules, Methodological Surveys Vol. 6., E. Reid, Editor.Protein Crosslinking. Volume 86A. Biochemical and Molecular Aspects, and Protein Crosslinking. Volume 86B.Nutritional and Medical Consequences, Mendel Friedman, Editor.Nutritional Factors in General Medicine: Effects of Stress and Distorted Diets.Mark D. Altschule. Charles C. Thoma

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00613.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00606.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY