摘要:

ABSTRACTPolyphenol oxidase from the peel of ripe mango fruit(Mangifera indica. Var. Raspuri)was purifed 126‐fold to homogeneity by ammoniun sulphate fractionation, column chromatography on Blue Sepharose CL‐6B and gel chromatography on Sephadex G‐200. It had an iso‐electric point (pI) of 4.1±0.2 and molecular weight of 137,000 daltons as determined by sodium dodecyl sulphate—polyacrylamide gel electrophoresis and gel filtration. It was more specific for catechol (than for other substatres tested) with a Km of 8.2 mM. 2‐mercaptoethanol, L‐cysteine, sodium diethyldithiocarbamate and thiourea were effective inhibitors of this enzyme. It had pH and temperature optima of 5.5 and 460C, respectively. It lost 50% activity by exposure to 850, 750and 650C for 3, 16 and 25.5 min, respectively. Copper content was one atom per mole of enzyme and copper was essential for its activity. Unlike most of the polyphenol oxidases, multiple forms were not detected in the

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1982.tb00303.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTi

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1982.tb00304.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTA study was made of whole soybeans, isolated protein bodies and a fraction consisting of globoid inclusions separated from protein bodies by centrifugation in order to observe the cellular location of phytate and to determine any indication of protein‐phytate interaction within the soybean cell. Microstructural and chemical evidence demonstrated phytic acid to be located in the protein bodies of the soybean, likely in the form of a soluble protein‐phytate salt with significant amounts specifically deposited in globoid inclusions. The probable existence of a protein‐cation‐phytate complexin situwas shown by gel filtration in which calcium and phosphorus was found to coelute with soluble proteins. The proteins involved in this interaction were tentatively identified as the 7S soybean f

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1982.tb00305.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTPhytate and bovine serum albumin were used in a model system to investigate the mechanism of their binding. Ultrafiltration studies using response surface design showed the association of protein and phytic acid to be highly pH dependent. Under acid conditions, the protein formed an insoluble complex with phytic acid. At pH 3.0, a binding constant of 2.3 times 105was obtained and it was calculated that there are 78 binding sites of the total 93 basic amino acid residues potentially available. This low pH complex was not disrupted at high temperatures but the presence of calcium ions caused dissolution of the precipitate. Calcium produced different effects at higher pH (>6). Soluble protein‐calcium‐phytic acid complexes were formed which were less stable to heat and dissociated above pH 10 at high ionic strength. Since this interaction occurred only in the presence of calcium, a salt linkage is implicated in which divalent cations simultaneously bind to the protein and phytic acid in the form of a soluble complex. It is proposed that either the addition of divalent cations at low pH or sequestering agents at high pH would best effect the removal of phytate from soy products by ultrafiltrat

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1982.tb00306.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTA study was conducted to determine the influence of pH on the chemical form of phytate in a commercial soy isolate and its effect on zinc bioavailability by monitoring weight gain in weanling rats. Ultrafiltration studies demonstrated that the free phytate content of soy isolate solutions was greatest at pH 5.0; above this the neutralization of soy isolates resulted in the formation of a soluble proteinphytate complex. The bioavailability of zinc from diets providing protein from egg, acid and neutral soy isolates and containing various levels of added zinc was measured. The growth of rats receiving zinc from the neutral soy isolate was significantly lower than that of rats deriving zinc from either the acidic soy isolate or egg white diets. It is proposed that the reduction in bioavailability of zinc caused by the neutralization of soy protein isolate is related to the formation of a protein‐zinc‐phytic acid complex resistant to hydrolysisin v

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1982.tb00307.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Book Reviews in this article.Flavor Research—Recent Advances.Edited by Roy Teranishi, Robert A. Flath and Hiroshi Sugisawa.Biotechnology—Volume 1: Microbial Fundamentals.Edited by H. J. Rehm and G. R

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1982.tb00308.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY