Animal tissues, enzyme extraction from

The cholinesterase to determine the toxic activity may be chosen (i) in pure form of commercial enzyme from animals in a water buffer solution or using biosensors, enzyme preparation impregnated into a rigid matrix that significantly activates the enzymic activity and (ii) in the form of crude extracts from plant or animal tissues. 

During the past 15 years data from experiments with different types of animal tissues and micro-organisms, using intact cells, crude extracts or purified enzymes, have firmly established the general occurrence of nucleotide reductases and have stressed their importance for DNA synthesis in essentially all types of rapidly growing cells [54]. It has been proposed that ribonucleotide diphosphates lose a hydroxide ion from C-2 to form a carbonium ion which is then stero-specifically reduced by a hydride ion derived from thioredoxin [54]. Adenosine diphosphate and guanosine diphosphate (as well as uridine and cytidine diphosphates) are reduced in this manner. 

Transglutaminases have just become recently available in larger quantities and high purity due to microbiological production of the enzyme instead of extraction from animal tissue. It can be expected that this enzyme will be used more frequently in the future for food and non-food applications. 

Heparin is a glycosaminoglycan extracted from animal tissues (porcine mucosa, beef lung, etc.). It is a mixture of molecules having a mean molecular weight of 15,000 Da. A pentasaccharide sequence found in approximately one third of the molecules binds to antithrombin in mammalian blood, enhancing its inhibitory effects on the enzymes thrombin, factor Xa, factor Vila, and factor IXa. The reaction is reversible, heparin being released after the antithrombin molecule binds to the procoagulant enzymes. Heparin binds to platelets, platelet factor-4 (which neutralizes it), histidine-rich GP vWp and a number of other proteins. Its half-life is about one hour in the circulation (18). Antibodies to heparin... 

A variety of extraction conditions employing methanol-water mixtures [11], phosphoric acid [79], and enzymes [80, 81] in combination with heating [82], sonification [83, 84], shaking [85-87], accelerated solvent extraction [88, 89], and MW-assisted extraction [90-93] have been used to isolate As species from marine algae and animal tissues. 

The use of metaphosphoric acid solutions for the extraction of ascorbic acid from plant and animal tissues was first proposed in 1935 (29). Metaphosphoric acid, along with trichloroacetic acid, remain as the reagents of choice. Besides the decreased tendency for hydrolysis of the lactone ring, metaphosphoric acid inhibits the catalytic oxidation of ascorbic acid by metal catalysts, such as copper and iron ions, and it inactivates the enzymes that oxidize ascorbic acid. Oxidation of ascorbic acid, which apparently is the result of the action of oxyhemoglobin, may occur when animal tissues are ground with metaphosphoric acid. This... 

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