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Protein nature, enzyme

For in vitro studies there are a number of compounds available to block protein phosphatase activity. Phosphate buffers inactivate all of these enzymes. Several naturally occurring toxins are potent inhibitors of PPPs, e.g., okadaic acid or microcystin, and are frequently used tools. PPM and PTP family members are not affected by these toxins. Vanadate containing solutions are competitive inhibitors of PTPs, pervanadate is an irreversible inhibitor of PTPs. [Pg.1014]

The nature of the molecular defect Is unclear and presumably lies In the repression mechanism for the gene controlling formation of the enzyme protein. Exposure to any of the drugs listed In Table V results In further marked de-repressIon of enzyme synthesis and severe porphyria. [Pg.277]

Enzymes are nature s catalysts. For the moment it is sufficient to consider an enzyme as a large protein, the structure of which results in a very shape-specific active site (Fig. 1.3). Flaving shapes that are optimally suited to guide reactant molecules (usually referred to as substrates) in the optimum configuration for reaction, enzymes are highly specific and efficient catalysts. For example, the enzyme catalase catalyzes the decomposition of hydrogen peroxide into water and oxygen... [Pg.6]

A naturally occurring animal model of PFK-M deficiency has been reported in English springer spaniels. Molecular analysis of this canine PFK-M deficiency disclosed that the enzyme deficiency was caused by a nonsense mutation in the penultimate exon of the PFK-M gene, leading to rapid degradation of a truncated (40 amino acid residues) and therefore unstable enzyme protein (SI8). [Pg.19]

Over the years of evolution, Nature has developed enzymes which are able to catalyze a multitude of different transformations with amazing enhancements in rate [1]. Moreover, these enzyme proteins show a high specificity in most cases, allowing the enantioselective formation of chiral compounds. Therefore, it is not surprising that they have been used for decades as biocatalysts in the chemical synthesis in a flask. Besides their synthetic advantages, enzymes are also beneficial from an economical - and especially ecological - point of view, as they stand for renewable resources and biocompatible reaction conditions in most cases, which corresponds with the conception of Green Chemistry [2]. [Pg.529]

Laufberger had tried to obtain the protein from horse liver, but it did not crystallize, and as he described to me when I met him in Prague some years ago, in those days everyone wanted to have protein crystals as a criteria of purity. Although James Sumner had crystallized jack bean urease in 1926, his preparations were somewhat impure, and it was only in the mid-1930s, when John Northrop and Moses Kubnitz showed that there is a direct correlation between the enzymatic activities of crystalline pepsin, trypsin and chymotrypsin that the protein nature of enzymes was generally accepted. [Pg.172]

Naturally-occurring food legume tannins are reported to interact with enzyme and non-enzyme proteins to form complexes that... [Pg.131]

The protein nature of enzymes was established through the seminal work of James Sumner. In 1926, Sumner succeeded in isolating the enzyme urease in crystalline form from jack bean meal. This was the first time in history that an enzyme had been obtained in crystalline, though not completely pure, form. Subsequently, Sumner established that the crystalline enzyme was a protein. Urease is an enzyme that degrades one of the human end products of nitrogen metabolism, urea, to ammonia and carbon dioxide ... [Pg.106]

Like many classic contributions to science, this spectacular advance was initially met with criticism and even derision. However, Sumner was not deterred he took his show on the road and, through demonstration, convinced many scientists of the protein nature of enzymes. Subsequently, a number of enzymes were crystallized in the 1930s by John Northrup and Moses Kunitz and were also shown to be proteins. These later preparations were essentially pure. Northrup and Kunitz demonstrated that enzyme activity paralleled the amount of protein present, laying the issue to rest. Sumner and Northrup shared the 1946 Nobel Prize in Chemistry. ... [Pg.106]

Fatty acid synthesis is catalysed in animals by the enzyme fatty acid synthase, which is a multifunctional protein containing all of the catalytic activities required. Bearing in mind the necessity to provide a specific binding site for the various substrates involved, and then the fairly complex sequence of reactions carried out, it raises the question of just how it is possible for this process to be achieved at the enzymic level. Nature has devised an elaborate but satisfyingly simple answer to this problem. [Pg.596]

The second aspect refers to the protein nature of enzymes. In 1894 Fischer (Fischer, 1909) stated that amongst the agents which serve the living cell the proteins are the most important. He was convinced that enzymes are proteins. The role of this key problem may be illustrated with a citation from Fruton (1979) ... the peptide theory was indeed only a hypothesis fifty years after Franz Hofmeister and Emil Fischer advanced it... (in 1902). The nature and stracture of proteins remained unknown throughout the 19th century remarkably, technological applications were nevertheless put into practice since the middle of the century (see above), based on their action, eventually recognized as catalysis, only. [Pg.10]

In addition to being necessary for all forms of life, biopolymers, especially enzymes (proteins), have found commercial applications in various analytical techniques (see Automated instrumentation, clinical chemistry Automated instrumentation, hemtatology Biopolymers, analytical techniques Biosensors Immunoassay) in synthetic processes (see Enzyme applications, industrial Enzyme applications in organic synthesis) and in prescribed therapies (see Enzyme applications, THERAPEUTICS IMMUNOTHERAPEUTIC AGENTS Vitamins). Other naturally occurring biopolymers having significant commercial importance are the cellulose (qv) derivatives, eg, cotton (qv) and wood (qv), which are complex polysaccharides. [Pg.94]

Enzyme inhibitors of a protein nature are of significant concern because of widespread occurrence. The most common of these affect the pancreatic enzymes, trypsin and chymotrypsin. and arc found in legumes, as well as in egg whites and potatoes. [Pg.673]

Enzymes are natural biomacromolecules that belong to the class of proteins. In an aqueous environment, they assume conformations that impart them with high... [Pg.18]

Leyser, O.H.M., Lincoln, C.A., Timpte, C., Lammer, D., Turner, J., Estelle, M. (1993). Arabidopsis auxin-resistance gene AXR1 encodes a protein related to ubiquitin-activating enzyme El. Nature (London) 364, 161-164. [Pg.241]

Enzymes are Nature s catalysts, facilitating all of the chemical reactions of metabolism. They bind a specific substrate in an entatic state moving it along the reaction coordinate towards the reaction transition state thus lowering the reaction activation energy. Enzymes are generally made of proteins and contain an active site, often based around a metal ion. [Pg.136]

This marked enzymic activity was exhibited by the preparation at a dilution of 1 100,000,000 parts of water. The most delicate tests for proteins are not valid at dilutions greater than about 1 100,000. Our preparation reacted like typical protein to the usual protein tests, but its own enzymic activity constituted a test for its presence which was 1000 times more delicate. Thus the f ailure of protein reactions in solutions enzymically active does not show that the enzyme is of other than protein nature in its chemical composition, although this negative conclusion has been erroneously drawn by some investigators and is repeated by many writers. [Pg.2]


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See also in sourсe #XX -- [ Pg.4 ]




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