摘要:

ABSTRACT4‐tert‐butylcatechol (t‐BC), at concentrations ranging from 0.033 to 16.6 mM, has a pronounced synergistic effect on the rate of DL‐DOPA oxidation to material absorbing at 475 nm (dopachrome) by mushroom tyrosinase. This phenomenon was found to be due to the ability of t‐BC‐quinone (formed by the oxidation of t‐BC by mushroom tyrosinase or by sodium periodate) to oxidize DL‐DOPA n

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1990.tb00832.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

ABSTRACT2,3,4‐Trihydroxyacetophenone (2,3,4‐THAP) can serve as a substrate for mushroom tyrosinase with a Kmvalue of 1.2 mM. The product(s) formed is yellow, characterized by a peak at 420–430 nm.A lag period in 2,3,4‐THAP oxidation to the yellow product(s) in the presence of ascorbate indicates that the initial product(s) is an o‐quinone of 2,3,4‐THAP. An oxime, characterized by a broad peak at 510–650 nm, is the likely product formed between o‐quinone of 2,3,4‐THAP and NH2OH. The ɛmof the o‐quinone of 2,3,4‐THAP was estimated to be 1.6 × 104M−1cm−1at 425 nm.During relatively long incubation periods, the peak of the yellow product(s) shifts from 420–425 nm to 430–440 nm; the solution remains yellow and transparent for at least a week and no precipitate is formed. The final yellow product(s) is probably a low molecular weight polymer of THAP

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1990.tb00833.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTA proteinaceous alpha‐amylase inhibitor from the cormel of taro(Colocasia esculenta)was purified by extraction, heat treatment, ammonium sulfate precipitation, and column chromatography on Sephadex G‐100, BioGel P‐30, and DE‐53 cellulose.This protein (aptly named esculentamin) was shown to be an acidic (pI = 4.4) glycoprotein with a carbohydrate content of 3.64% and a molecular weight of 11,800 daltons. Esculentamin activity was essentially stable to boiling for 3 h (pH 7.0), to a pH range of 2.0 to 12.0 (at 4°C), and to 6 M guanidine hydrochloride and 8 M Urea. Amino acid analysis indicated a predominance of acidic over basic amino acids, while side‐by‐side neutral and alkaline absorption spectra strongly suggested a lack of tryptophan.“Bifunctional” inhibitory activity towards both α‐amylase and proteases was not observed with esculentamin (i. e., it did not inhibit the several proteases tested, viz. tryp

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1990.tb00834.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTArachin and conarachin were purified from phosphate buffer (0.20 and 0.05 M, pH 7.9) extracts using ammonium sulfate fractionation at 40 and 60–85% saturation, respectively. Characterization on SDS‐PAGE gel revealed that arachin was composed of five major subunits whereas conarachin consisted of one major subunit. Methionine, lysine, and 1/2 cystine content of conarachin was, respectively, about three‐, two‐ and two‐fold higher than in arachin. During dry roasting of whole peanut kernels and lyophilization of peanut extracts at 150°C for 60 min, the nitrogen soluble indexes of arachin and conarachin decreased with time. Changes in conarachin were comparatively higher than those in arachin. When buffered extracts of kernels were subjected to boiling water bath cooking for 60 min, the native protein patterns of arachin and conarachin, as shown on gradient PAGE, varied significantly with heating time. Subunits of arachin detected on SDS‐PAGE did not qualit

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1990.tb00835.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTCrude protein, extracted protein, and nonprotein nitrogenous substances were quantified in 55 varieties of common dry beans. Crude protein (% N x 6.25) on a dry basis varied from 23.01 to 35.22%, with a mean value of 28.51%. Methionine varied from 0.40 to 1.73% of the crude protein with a mean value of 0.80%. The ratio of globulin/albumin ranged from 1.00 to 3.31. Thirty percent of the total nitrogen was of low MW and was lost in the dialysis (MW cut off 8,000 daltons). Electrophoretic patterns (PAGE) revealed from 3 to 11 bands in the globulin fraction and 4 to 11 in the albumin fraction. Trypsin and chymotrypsin inhibitory activity was much higher in the albumin fraction than in the globulin fraction. The globulin fraction from most of the varieties was more inhibitory against trypsin than chymotrypsin. On the other hand, in the albumin fraction of the majority of the varieties the activity was stronger against chymotrypsin. Hemagglutination titer for 57 varieties ranged from 1024 to 32. Eight varieties had titers of 1024 and only four had titers of 32.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1990.tb00836.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Book reviewed in this article:Probing Bioactive Mechanisms. Edited by P. S. Magee, D. R. Henry, and J. H. Block.Protein Quality and the Effects of Processing. Food Science and Technology Series No. 29. Edited by R. Dixon Phillips and John W. Finley.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1990.tb00837.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1990.tb00831.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY