摘要:

ABSTRACTMuscle proteases active at neutral and alkaline pH's include calcium‐activated neutral proteases, heat‐activated thiol proteases, serine proteases, and metallo‐proteases. They participate to different extents in postmortem degradation of fish muscle myofibrillar and scaffold proteins. Their activity in fish, the presence of endogenous activators and inhibitors, pH, and temperature. Recent studies indicate that neutral and alkaline proteases have more impact on the postmortem deterioration in quality of fish muscles than the cathepsins active at acid pH. Significant quality losses are caused by enzymatic collagen degradation in raw tissues and by heat‐activated enzymes in fi

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1996.tb00561.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTPlant phenolics are secondary plant products, sometimes synthesized as chemical defenses to microorganisms, and also serve as potential sources of food preservatives. In this study, we have investigated the extent of stimulation of total phenolics and rosmarinic acid (RA) levels in threein vitroshoot culture‐based thyme clonal lines in response to a novelPseudomonas spp.previously isolated from oregano tissue cultures. Clonal lines chosen for this study were the high phenolic line T‐12 and the medium‐ and low‐phenolic lines T‐16G and M‐3. Results indicate that different strains ofPseudomonasstimulated total phenolic levels and RA accumulation to varying degrees. Mucoid strain M4 elicited the highest levels of RA in clonal line T‐12 on day 25. A moderate degree of RA stimulation in response to M4 was observed in clonal line M‐3. Mucoid strain F elicited the highest total phenolic levels in T‐12 on day 25. Nonmucoid strain NMA elicited stimulation of total phenolic compounds and RA to some degree only in clonal line T‐16G. A 30 day time course analysis in line T‐12 indicated that strains F and NMA elicited the highest phenolic levels. RA synthesis appeared to be stimulated in response to M4 at later stages of growth and reduced stimulation was apparent in response to F and NMA. The mechanical rigidity of T‐12 shoots appeared to be highest in response to mucoid strain M4, indicating the possibility of increased lignin formation. ThisPseudomonas‐thyme clonal system provides a foundation to investigate the microbially‐elicited stimulation of biosynthetic pathways leading to novel anti

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1996.tb00562.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTMonoclonal antibody Fab fragments which bind epitopes in the rod domain of skeletal muscle myosin had specific effects on the solubility properties of chicken muscle myosin in vitro. Two antibodies (NA4 and 5C3), which bind at the C‐terminal portion of the rod domain caused myosin to remain soluble and monomeric in 0.1 M KCl, pH 7.2, conditions in which myosin normally aggregates into filamentous structures. Other antibodies (EB165 and AB8), which bind in the middle of the rod did not alter either myosin solubility or the morphology of the myosin assemblies formed. These results demonstrate the importance of the C‐terminus of the myosin rod as a domain involved in regulating myosin interactions and solubil

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1996.tb00563.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTMany vegetables exhibit a firming effect after precooking at a temperature between 50 and 70C. This effect has generally been attributed to the action of endogenous pectinesterase which hydrolyzes the methyl ester linkages in pectin molecules. The resulting free carboxyl groups then form Ca‐bridges between pectin molecules. We have shown, by using the pectinesterases of pea sprouts, that the enzymes catalyzed not only the hydrolysis of the methoxyl groups of pectin molecules, but also a tranacylation reaction of the galacturonic acyl groups from methanol to other hydroxyl groups of pectin. The latter reaction results in the formation of new ester linkages between pectin molecules, which also contributes to the firming of the tissue. The pectinesterases have been separated into four isozymes, PE1, PE2, PE3, and PE5. The isozymes exhibited similar transacylation activity, with the exception of PE5 that did not catalyze transacylatio

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1996.tb00564.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe effects of trinitrophenyl (TNP) derivatives of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) on the coupled activities of the tonoplast ATPase in corn roots were investigated. The addition of TNP‐ATP at micromolar concentrations (0.5–0.25 mM) significantly decreased both the ATP hydrolytic activity and the coupled proton pumping activity. The presence of TNP‐ATP resulted in an increased Km for ATP and a reced maximum enzyme velocity. Unlike TNP‐ATP that strongly inhibited proton transport at low concentration, TNP‐ADP inhibited this activity only slightly. TNP‐AMP stimulated proton transport at low concentrations. ADP and AMP inhibited the initial rate of proton transport in a different manner. The concentrations required to inhibit half of the initial rate of proton transport activity for ADP and AMP were 80 μM and 2 mM, respectively. The results suggest that tonoplast vesicles may contain at least two kinds of nucleotide b

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1996.tb00565.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Book reviewed in this article:EMULSIONS AND EMULSION STABILITY. Edited by Johan Sjölom.THE FOOD CHEMISTRY LABORATORY. A Manual for Experimental Foods, Dietetics, and Food Scientists. Connie M. Weaver.IMMUNOASSAYS FOR RESIDUE ANALYSIS. FOOD SAFETY. ACS Symposium Series 621. Edited by R.C. Beier and L.H. Stanker.FLAVOR‐FOOD INTERACTIONS. Edited by Robert J. McGorrin and Jane V. Leland.FOOD, THE CHEMISTRY OF ITS COMPONENTS, 3RD EDITION. T.P. Coultate.HYDROGELS AND BIODEGRADABLE POLYMERS FOR BIOAPPLICATIONS. Edited by Raphael M. Ottenbrite, Samuel J. Huang, and Kinam Pa

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1996.tb00566.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY