摘要:

ABSTRACTThe two main trypsin‐chymotrypsin isoinhibitors previously purified from lentils(Lens culinarisMedik.), LCI‐1 and LCI‐4, inhibited one mol of human trypsin (1.05 and 1.00), more than one mol of bovine trypsin (1.53 and 1.38) and human chymotrypsin (1.70 and 1.43) as well as less than one mol of bovine chymotrypsin (0.62 and 0.54, respectively) per mol of inhibitor. Complex formation, together with chemical and enzymatic modification studies, showed that they were Bowman‐Birk inhibitors with two independent reactive sites. One of these sites, mainly reacting with trypsin, contained arginine and bound tightly to bovine trypsin, less tightly to human trypsin and loosely to human chymotrypsin. The other reactive site, preferring chymotrypsin, contained tyrosine and bound tightly to human chymotrypsin, less tightly to bovine chymotrypsin and loosely to bovine trypsin. The amounts of bound enzyme exceeding one mol per mol of inhibitor reacted with the “wrong” sites: bovine trypsin with the chymotrypsin‐reactive and human chymotrypsin with the trypsin‐reactive one. The much higher inhibition of human chymotrypsin compared to that of bovine chymotrypsin resulted from a combination of two effects: the additional binding of human chymotrypsin at the “wrong” reactive site and the weak binding of the

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1989.tb00387.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe kinetics of degradation of the essential amino acid lysine have been determined in compressed lysine‐glucose‐cellulose models exposed to expected and accelerated storage test temperature extremes. The compressed models were stressed at 40, 50 and 60°C at low water activities in the range of 0.19 to 0.21 for various periods. Six different parameters (color, fluorescence, reducing capacity, furosine, glucose and lysine) were employed to follow the course of the reaction. The t 1/2 values estimated from first order plots for lysine degradation in these models were 370, 13 and 1.5 h at 40, 50 and 60°C, respectively. An Arrhenius plot relating the first order reaction rate constant with the temperature has yielded a high activation energy of 57 kcal/mol, and a high Q10 of 14, which is indicative of large temperature dependence of lysine degradation in these compressed models. There was poor correlation of fluorescence and of color increase with lysine loss. Good correlations were obtained between lysine loss and the increases in reducing capacity and furosine at 50 and

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1989.tb00388.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTChilling injury (CI) is a physiological defect of plants and their products that results in reduced quality and loss of product utilization following exposure to low but nonfreezing temperatures. To design more effective control strategies and maximize shelf‐life, it is necessary to develop an understanding of the biochemical mechanism(s) responsible for the initiation of CI. Despite considerable efforts in this field of study, there is no general agreement on the cause or nature of CI, or even the primary event(s) triggering low temperature damage.The first unified theory to explain CI was founded on low temperature induced membrane lipid phase transitions leading to a loss of membrane integrity and physiological dysfunction. This was modified to account for the observation that the level of certain high melting phospholipids appears to be related to the chill sensitivity of many plant tissues. Membranes and changes in their physical characteristics are further implicated as having a role in CI by the discovery that chilling stress evokes an elaborate membrane retailoring response that leads to increased fluidity at reduced temperatures.Others have postulated that CI results from the direct effect of reduced temperatures on enzymes or the indirect effect of membrane perturbations on intrinsic enzymes. The redistribution of cellular calcium has most recently been advanced as the primary transducer of CI. The weight of this theory rests on the role of calcium as a secondary messenger for many cellular functions. In this review it is also speculated that lipid peroxidation may have a role in the development of irreversible injury during low temperature stress. Its effect would be similar to the senescent processes of free radical damage to tissue and progressive membrane rigidificatio

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1989.tb00389.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Book reviews in this article:Brewing Microbiology. Edited by F. G. Priest and I. Campbell.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1989.tb00390.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY