摘要:

ABSTRACT2, 4, 5‐THBP (2, 4, 5‐trihydroxybutyrophenone) is a substrate for mushroom tyrosinase with a Kmvalue of 1.00 mM. The final product(s) formed is red (λ.max480–490 nm) and it is rather stable with time. An intermediate red product(s), having a maximum at λ 505–515 nm, was detected and the time course of its conversion to the final red product(s) was studied. The data suggest that the intermediate red product(s) is 2, 4, 5‐THBP‐quinone which is converted to colorless polymerized 2, 4, 5‐THBP‐OH, which is then oxidized to a red polymerized 2, 4, 5‐THBP‐quinone(s), which is the

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTTwo phenoloxidase (PPO) isoforms were purified from Taiwanese black tiger shrimp (Penaeus monodon) purified via ammonium sulfate precipitation and high performance hydrophobic interaction chromatography on phenyl Sepharose CL‐4B. Optimal DL‐ã‐3, 4‐dihydroxyphenylalanine (D, L‐DOPA) oxidation by these isoforms was observed to occur at pH 6.0, and at 45°C. The isoforms showed both mono‐ and di‐PPO activities, and preferential medabolism of both monoand di‐phenolic substrates lacking a carboxyl group either directly attached to the ring, or in the side chain moiety of the p

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTSoybean (Glycine max. L.) glycinin (11S) purified by the Thanh and Shibasaki method (J. Agric. Food Chem. 24, 1117–1121 (1976)) is usually 90% pure. One of the impurities present in such glycinin preparations is the sulfur‐rich salt‐soluble globulin (SRP). The SRP which co‐purifies with glycinin is resolved when such glycinin preparations are chromatographed on a DEAE DE‐53 anionexchange column. It represented up to 5.32% of the total protein recovered. Hydrophobic and disulfide exchange interactions are the likely forces responsible for the co‐purification of SRP wi

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00142.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTTwo electrophoretically homogeneous proteinases designated proteinase A and B were isolated from anchovy viscera. Purity was increased 17.7 and 24.6‐fold with approximately 1.9 and 1.8% yield for proteinases A and B, respectively. The maximum caseinolytic activity was found to be at pH 9.4 for proteinase A and at pH 9.6 for proteinase B at the optimum temperature of 48°C. The molecular weights of proteinase A and B were determined to be 27, 300 and 25,100 D, respectively, using Sephadex G‐100 gel filtration. The amino acid profiles of the enzymes were similar and relative proportion of amino acid residues was comparable to that in bovine pancreatic α‐chymotrypsin. Proteinase A and B were identified as α‐chymottypsin‐like serine proteases by inhibitor and substrate specificity studies. Apparent Km(Km′) values of proteinase A and B for benzoyl‐L‐tyrosine ethyl ester were 4.6 × 10−4M and 1.2

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00143.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTModel systems containing taurine or proline mixed with glucose at pH 6.4 were adjusted for water activity (Aw) to 0.99, 0.90, 0.84, 0.75 and 0.60 with celite. The browning rates measured during 96 h at temperatures between 5° and 45°C increased with increased temperature and reduced water activity. The model system containing taurine had a higher browning rate than that with proline at the same Aw and temperature. The browning rate with taurine at Aw = 0.60 increased 34 times at 45°C and 7 times at 35°C compared to that at 25°C. Decreases in Aw from 0.90 to 0.60 resulted in increased browning rate, 4.1 times at 45°C and 1.3 times at 35°C. The browning rate in model systems with proline followed the same pattern. Temperature had a more pronounced effect on browning rate than Aw. Browning was very slow in model systems at temperatures below 25°C.Evidence is provided that the Maillard reaction occurred in the mantle of squid(Illex argentinus)during air drying at 35°C. Dehydration resulted in loss of 50% of the taurine (from 22.3 to 11.6 mmoles/100g dry mass) and more than 60% of the proline (from 23.4 to 8.9 mmoles/100g dry mass). Total free amino acids remained unchanged when the moisture level was above 50% or Aw = 0.95. The browning intensity of the squid mantle increased 5 fold during drying. Taurine and proline were digested most at water activity above 0.95, while other amino acids were lost at a greater rate in the intermediate water activi

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00144.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00145.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY