摘要:

ABSTRACTThe molecular and enzymatic properties of the extensively studied enzyme cathepsin D are reviewed and additional information concerning its activity presented. Cathepsin D at pH 5.5 (37°C) degraded several myofibrillar proteins. The most rapidly hydrolyzed included titin and perhaps nebulin, myosin heavy chain, and M and C‐proteins. The effects of cathepsin D on myofibrillar structure under these conditions included reduction in A band width, cleared central region in the A band, and dislocation of the Z line. Temperature was found to exert a strong influence on activity of cathepsin D and maximum activity was observed at 45°C with both muscle and hemoglobin substrates. Activity was evident at even higher temperatures and approximately 49% remained at 55°C (hemoglobin assay). Low temperature (i.e.,<15°C) however, has been observed to result in almost complete inactivity of the enzyme. The implications of this information for involvement of cathepsin D in postmortem proteolysis and tenderization were disc

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1989.tb00391.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1989.tb00392.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTAcetylation of ε‐amino groups of lysine residues changed conformation of glycinin isolated from soybean, the extent of which depended upon the degree of modification. Soy glycinin with lysine residue modifications of 0%, 28%, 65%, 85%, and 95% were used for the experiment. Accessibility of tyrosine and tryptophan residues, which were shown to increase as modification percent increased, were detected using uv absorption spectra and fluorescence spectra, respectively. Surface hydrophobicity was found to increase more than two times over native glycinin, when lysine residues were excessively modified to above 95%. Masking of charged lysine residues, exposure of hydrophobic interior, and subunit dissociation should have contributed to the increase. Enthalpy, as obtained from differential scanning calorimetry, dropped from 3.6 callg native protein to 0 callg protein, when lysine residues were acetylated above 65%. implicating complete denaturation. The hydrolytic rates, using α‐chymotrypsin, increased initially, then decreased at more than 65% lysine modific

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1989.tb00393.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTA 23,500 dalton protease was isolated from the pyloric ceca of Atlantic cod by the successive steps of ammonium sulfate fractionation, acetone precipitation and affinity chromatography. The protein fraction recovered after affinity chromatography migrated as one band in both Davis and Laemmli gels. The protease was classified as trypsin (EC 3.4.21.4) on the basis of its substrate specificity, molecular weight and response to known trypsin inhibitors. For trypsin hydrolysis of benzoyl‐DL‐arginine p‐nitroanilide, the substrate turnover number was 250 BAPA units per micromole trypsin (25°C), Km1was 1.48 mM, theArrhenius energy of activation (Ea) was 8.9 kcal/mol, and the free energy of activation (ΔG*) was 12.8 kcal/mol. The Vmax for the hydrolysis of tosylarginine methyl ester was 18,210 TAME units per micromole trypsin and the Km1for the same reaction was 0.22 mM

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1989.tb00394.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTTwo double‐headed isoinhibitors of endogenous alpha‐amylase and subtilisin have been purified from triticale by immobilized copper affinity chromatography followed by S‐Sepharose Fast Flow ion exchange chromatography and preparative isoelectric focusing on a sucrose density gradient ampholyte column. The inhibitors had isoelectric points at pH 7.25 and 6.95, and were present in triticale grains in approximately equal amounts. Both proteins, designated inhibitor 7.25 and inhibitor 6.95, have been purified to homogeneity as assessed by nondenaturing polyacrylamide gel electrophoresis (PAGE) at pH 8.3. They also showed approximately 90% purity as determined by size exclusion limit FPLC. Their properties were similar to the endogenous alpha‐amylase/subtilisin inhibitors found in wheat and barley, since they were active against cereal alpha‐amylases and subtilisin and they were inactive against salivary and bacterial alpha‐amylases as well as against trypsin. Apparent MW of both inhibitors was 20 kilodaltons as estimated from sodium dodecyl sulfate‐PAGE under reducing conditions. No carbohydrate was detected in isoinhibitor preparations. The triticale alpha‐amylase‐triticale inhibitor systems studied revealed a mixed type of inhibition with apparent dissociation constant (Ki) values of 6.2 and 5.8 nM for the inhibitor 7.25 and inhibitor 6

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1989.tb00395.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Book reviewed in this article:The Flavonoids: Advances in Research Since 1980. Edited by J. B. Harbone

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1989.tb00396.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY