5 - enzymic splitting

An enzyme digest is the term applied to a process whereby a peptide or protein is mixed with a selected enzyme under favorable conditions to allow reaction to occur. The enzyme splits the peptide or protein into smaller units that are easier to identify. 

A very large number of volatile substances have been identified in fresh tea leaf.64 Substances present at the highest levels include the ubiquitous leaf aldehyde, trans-2-hexenal, and leaf alcohol, cis-3-hexenol. Both arise from cis-3-hexenal, which is biosynthesized from linoleic acid in leaf as a result of enzymic splitting.65... 

The dephosphorylation of myosin requires the activity of myosin phosphatase. Located in cytoplasm of the smooth muscle cell, this enzyme splits the phosphate group from the myosin. Dephosphorylated myosin is inactive crossbridge cycling no longer takes place and the muscle relaxes. 

Saliva begins the process of chemical digestion with salivary amylase. This enzyme splits starch molecules into fragments. Specifically, polysaccharides, or starches, are broken down into maltose, a disaccharide consisting of two glucose molecules. Salivary amylase may account for up to 75% of starch digestion before it is denatured by gastric acid in the stomach. 

Cammack, R. (1995) Redox enzymes. Splitting molecular hydrogen. Nature, 373, 556-7. 

Hengstenberg, W., Egan, J. B. and Morse, M. L. 1967. Carbohydrate transport in Staphylococcus aureus. V. The accumulation of phosphorylated carbohydrate derivatives and evidence for a new enzyme-splitting lactose phosphate. Proc. Natl. Acad. Sci. USA 58, 274-279. 

Enzymes depolymerizing polysaccharides may have an endo or an exo action pattern, and may hydrolyze, or cleave by elimination. Both the conformation of the polysaccharide and the active site of the enzyme need to be considered in the enzyme-glycan interaction. endo-Enzymes split, by a random type of depolymerization, glycosidic bonds situated internally in... 

The first, X-ray diffraction results obtained favor the T conformation. In collaboration with the Laboratory of the Physics of Solids at the University of Lille, we have undertaken an initial series of experiments that concern the structures of oligosaccharides of low molecular weight that exist in complete glycans, as prepared from glycoprotein-osis urines or by chemical and enzymic splitting of different glycans. 

The first-named enzyme binds two thiosulfate molecules together to form tetrathionate, while the other two enzymes split thiosulfate into sulfide and sulfite. 

Since it is well established that the P-chiral phosphorothio-ates serve as effective probes in mechanistic studies for the phos-phoryl group transfer enzymes /16/, we turned our attention to the application of diastereomeric 8 (B=Thy, Ar=pN02C6Hi -,/17f) to elucidate the mode of action of spleen phosphodiesterase (SPDE, EC 3.1.1. 18). This enzyme splits the phosphodiester bonds to yield nucleoside 3 -phosphates. In the case of it was expected that its SPDE-catalyzed hydrolysis in 180 H 2O medium leads to P-chiral thymidine 3 - 180 phosphorothioate. On the contrary to our expectation the main product of this reaction was thymidine cyclic 3 ,5 - Rp phosphorothioate (10) /6/. By treatment of 8 under the same conditions, but in the absence of the enzyme, no trace of J 0 was detected. ... 

J. S. D. Bacon, private communication to the author . .. we have yet to find an enzyme splitting a disaccharide that does not show some transferring power, June, 1951. 

The enzyme splitting both adenosine-tetraphosphate and guanosine-tetraphosphate was purified to homogeneity from yellow lupin seeds (Guranowski et al., 1997). The polypeptide of 25 kDa catalysed the hydrolysis of nucleoside-5 -tetraphosphate to nucleoside triphosphate and P , and hydrolysed PolyP3, but neither pyrophosphate nor PolyPs The divalent carions Mg2+, Co2+, Ni2+ or Mn2+ were required for the reaction. 

C. Neuherg and H. Fischer (1938). Enzymic splitting of triphosphoric acid. II. Hydrolysis by means of an enzyme found in Aspergillus niger and yeast. Analytical reactions of triphosphate. 

Figure 1-27 Enzymic Splitting of Lecithin in a Mixture of Barley Malt and Lecithin Stored at 30°C and Different Water Activities. Lower aw values were changed to 0.70 after 48 days. Source From L. Acker, Water Activity and Enzyme Activity, Food TechnoL, Vol. 23, pp. 1257-1270, 1969.

Restriction Enzymes Split DNA into Specific Fragments... 

Figure 3-13 Comparison of filtration and scintillation proximity assays, a. In filtration assay, the enzyme, substrate, and inhibitor are mixed the uninhibited enzyme splits the radioactive portion ( ) off the substrate, and filtering the mixture, followed by measuring the radioactivity of the filter, tells how much inhibition has occurred, b. In SPA, the same mixture is treated with resin beads containing a scintillant that fluoresces only in close proximity to the radioactive source Any radioactivity that was split off by the enzyme does not need to be filtered In SPA.

The two enzymes differ in specificity toward some substrates while behaving similarly toward others. The serum enzyme acts on benzoylcholine but cannot hydrolyze acetyl-p-methylcholine the red cell enzyme acts on the latter but not on the former. The red cell enzyme splits only choline esters aryl or alkyl esters are not attacked. The red cell enzyme is inhibited by its substrate, acetylcholine, if present at about 10 mol/L the serum enzyme is not inhibited by this substrate. 

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