A Study of the "Lipoxidase" in the Flesh of British Columbia Herring

1952 ◽  
Vol 9 (8) ◽  
pp. 393-416 ◽  
Author(s):  
M. M. R. Khan
Keyword(s):  
British Columbia ◽  
Unsaturated Fatty Acids ◽  
Dark Muscle ◽  
Active Centre ◽  
Nitrogenous Compounds ◽  
Sulphydryl Group ◽  
Optimal Activity ◽  
Highly Active ◽  
Enzyme Substrate ◽  
Kinetics Of

From the dark muscle of British Columbia herring a highly active enzyme capable of peroxidizing non-conjugated unsaturated fatty acids was isolated. This "lipoxidase", which was shown to be a nitrogenous complex possessing no heavy metals or sulphydryl group as the active centre, is heat-labile and can act only in presence of activators such as certain iron-containing organic nitrogenous compounds. Two such compounds, namely haemoglobin and cytochrome "c" were isolated. The enzyme exhibits optimal activity at 15 °C. and pH 6.9. There is also an optimal concentration of enzyme, substrate, and of the activators for maximal enzyme activity. The presence of the activators appears to change the kinetics, of the reactions. The inhibition of the enzymic reaction brought about by cyanide and azide is possibly due to the inactivation of the iron-containing activators rather than of the enzyme itself.

scholarly journals Benzofuroxan as a thiol-specific reactivity probe. Kinetics of its reactions with papain, ficin, bromelain and low-molecular-weight thiols

1977 ◽  
Vol 167 (3) ◽  
pp. 799-810 ◽  
Author(s):  
M Shipton ◽  
K Brocklehurst
Keyword(s):  
High Electron ◽  
Thiol Groups ◽  
Active Centre ◽  
Enzyme Substrate ◽  
Mechanistic Basis ◽  
A Site ◽  
Kinetics Of ◽  
State Concentration ◽  
Imidazolium Ion ◽  
Active Centres

1. The characteristics of benzofuroxan (benzofurazan 1-oxide, benzo-2-oxa-1,3-diazole N-oxide) that relate to its application as a reactivity probe for the study of environments of thiol groups are discussed. 2. To establish a kinetic and mechanistic basis for its use as a probe, a kinetic study of its reaction with 2-mercaptoethanol was carried out. 3. This reaction appears to proceed by a rate-determining attack of the thiolate ion on one of the electrophilic centres of benzofuroxan (possibly C-6) to provide a low steady-state concentration of an intermediate adduct; rapid reaction of this adduct with a second molecule of thiol gives the disulphide and o-benzoquinone dioxime. 4. The effects of the different types of environment that proteins can provide on the kinetic characteristics of reactions of thiol groups with benzofuroxan are delineated. 5. Benzofuroxan was used as a thiolspecific reactivity probe to investigate the active centres of papain (EC 3.4.22.2), ficin (EC 3.4.22.3) and bromelain (EC 3.4.22.4). The results support the concept that the active centres of all three enzymes either contain a nucleophilic thiolate ion whose formation is characterized by a pKa of 3-4 and whose reaction with an electrophile can be assisted by interaction of a site of high electron density in the electrophile with active-centre imidazolium ion of pKa 8-9, or can provide such ions by protonic redistribution in enzyme-reagent or enzyme-substrate complexes.

Specific features of the kinetics of gas-evolving reactions on highly active electrodes

1989 ◽  
Vol 34 (7) ◽  
pp. 929-942 ◽  
Author(s):  
V.V. Losev ◽  
N.Ya. Buné ◽  
L.E. Chuvaeva
Keyword(s):  
Highly Active ◽  
Kinetics Of

scholarly journals Kinetics Of The Enzymatic Transesterification Of Tuna Oil Catalyzed By Immobilized Candida Rugose Lipase To Produce Structured Lipid High In Omega-3 Fatty Acids

2018 ◽  
Vol 73 ◽  
pp. 06008 ◽  
Author(s):  
Amalia Rizka ◽  
Wahyuningsih Wahyuningsih ◽  
Broto RTD Wisnu ◽  
Endy Yulianto Mohamad ◽  
Rama Devara Hafizh ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fish Oil ◽  
Lauric Acid ◽  
Unsaturated Fatty Acids ◽  
Structured Lipids ◽  
Structured Lipid ◽  
Omega 3 ◽  
Enzymatic Transesterification ◽  
Substrate Ratio ◽  
Kinetics Of

Structured lipid containing Medium Chain of Fatty Acid (MCFA) at outer position and Poly-Unsaturated Fatty Acids (PUFA) at sn-2 position has nutritional value and excellent absorption. In this research, structured lipids was synthesized directly through enzymatic acidolysis between fish oil and lauric acid and catalyzed by specific lipase from immobilized 1.3 Candida rugose. The kinetics of enzymatic transesterification reactions catalyzed by immobilized Candida rugose was studied. To obtain the optimal condition, the factor substrate ratio of fish oil : lauric acid and reaction time were investigated. Simple mathematical model for DAG synthesis through transesterification mechanisms have been developed. The results showed that the parameters obtained had a good sensitivity. It was found that the kinetic model well describes the behavior of the reaction as the influence of the initial ratio of reactants.

Development of Torrefaction Kinetics for British Columbia Softwoods

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Jianghong Peng ◽  
Xiaotao T. Bi ◽  
Jim Lim ◽  
Shabab Sokhansanj
Keyword(s):  
British Columbia ◽  
Weight Loss ◽  
Kinetic Model ◽  
Residence Time ◽  
Order Reaction ◽  
First Order Reaction ◽  
Chemical Components ◽  
First Order ◽  
One Step ◽  
Kinetics Of

Torrefaction is a thermal treatment without air or oxygen in the temperature range of 473-573 K. The pyrolysis kinetics of three chemical components (cellulose, hemicelluloses, and lignin) and wood at low temperatures of relevance to torrefaction conditions have been reviewed. A series of thermogravimetric (TG) experiments have been carried out to study the intrinsic torrefaction kinetics of major chemical components and British Columbia (BC) softwoods. The weight loss during BC softwood torrefaction was found to be mainly associated with the decomposition of hemicelluloses, although there was also certain degree of decomposition of cellulose and lignin. The weight loss of the BC softwoods during torrefaction could be approximately estimated from the chemical composition of wood species and the weight loss data for torrefaction of pure cellulose, hemicelluloses, and lignin, respectively. Based on the fitting of the TG curves of BC softwoods and three chemical components, two different torrefaciton models were proposed. The simple one-step (single-stage) kinetic model with the first order reaction can predict the reaction data reasonably well over the long residence time, with the final sample weight being strongly related to the torrefaction temperature. A two-component and one-step first order reaction kinetic model, on the other hand, gave improved agreement with data over short residence time, and can be used to guide the design and optimization of torrefaction reactors over the weight loss range of 0 to 40% at the temperature range of 533-573 K, which covers the typical range of industrially relevant operations.

scholarly journals The kinetics of hydrolysis of some extended N-aminoacyl-l-arginine methyl esters by human plasma kallikrein. Evidence for subsites S2 and S3

1982 ◽  
Vol 203 (1) ◽  
pp. 149-153 ◽  
Author(s):  
P R Levison ◽  
G Tomalin
Keyword(s):  
Human Plasma ◽  
Methyl Esters ◽  
Plasma Kallikrein ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
Rate Limiting Step ◽  
Kinetics Of Hydrolysis ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Hydrolysis Of

Subsites in the S2-S4 region were identified in human plasma kallikrein. Kinetic constants (kcat., Km) were determined for a series of seven extended N-aminoacyl-L-arginine methyl esters based on the C-terminal sequence of bradykinin (-Pro-Phe-Arg) or (Gly)n-Arg. The rate-limiting step for the enzyme-catalysed reaction was found to be deacylation of the enzyme. It was possible to infer that hydrogen-bonded interactions occur between substrate and the S2-S4 region of kallikrein. Insertion of L-phenylalanine at residue P2 demonstrates that there is also a hydrophobic interaction with subsite S2, which stabilizes the enzyme-substrate complex. The strong interaction demonstrated between L-proline at residue P3 and subsite S3 is of greatest importance in the selectivity of human plasma kallikrein. The purification of kallikrein from Cohn fraction IV of human plasma is described making use of endogenous Factor XIIf to activate the prekallikrein. Kallikreins I (Mr 91 000) and II (Mr 85 000) were purified 170- and 110-fold respectively. Kallikrein I was used for the kinetic work.

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