Enzyme example

Arachin, the counterpart of glycinin in peanuts, consists of subunits of 60,000—70,000 mol wt which on reduction with 2-mercaptoethanol yield polypeptides of 41,000—48,000 and 21,000 mol wt (17) analogous to the behavior of glycinin. In addition to the storage proteins, oilseeds contain a variety of minor proteins, including trypsin inhibitors, hemagglutinins, and enzymes. Examples of the last are urease and Hpoxygenase in soybeans. 

Another characteristic of enzymes is their frequent need for cofactors. A cofactor is a nonproteia compound that combines with the otherwise iaactive enzyme to give the active enzyme. Examples of cofactors are metal ions such as Ca ", Cu ", Co ", Fe ", and and organic molecules such as... 

A prodrag is a drug that is not by itself pharmacologically active but needs metabolic activation by an enzyme. Examples are the cytostatic cyclophosphamide, which is activated by hydroxylation catalyzed by CYP2B6, or HMGCoA reductase inhibitor, lovastatin, which contains... 

Although the molecular details of enzyme mechanisms are complex, the kinetic behavior of many enzymatic processes is first order in both the substrate and the enzyme. Example shows that the mechanism just outlined is consistent with this kinetic behavior. 

A common way to benefit from the ability to combine different molecular orbital methods in ONIOM is to combine a DFT or ab-initio description of the reactive region with a semi-empirical treatment of the immediate protein environment, including up to 1000 atoms. Due to the requirement for reliable semi-empirical parameters, as discussed in Section 2.2.1, this approach has primarily been used for non-metal or Zn-enzymes. Examples include human stromelysin-1 [83], carboxypeptidase [84], ribonucleotide reductase (substrate reaction) [85], farnesyl transferase [86] and cytosine deaminase [87], Combining two ab-initio methods of different accuracy is not common in biocatalysis applications, and one example from is an ONIOM (MP2 HF) study of catechol O-methyltransferase [88],... 

Product Measured Species Monitored Couplinq Enzymes Examples... 

Effect of immobilization on the dynamic properties of enzymes. Examples of three different experimentally imposed conditions include (a) enzyme and substrate are present in an aqueous solution (b) enzyme and substrate are immobilized on or within a solid support and (c) immobilized enzyme acts on a substrate present within an aqueous solution. The rate laws and curves that are presented below each diagram indicate the expected rate behavior. (From K. J. Laidler P. S. Bunting (1982) Meth. Enzymol. 64, 229.)... 

The use of enzymes and whole cells as catalysts in organic chemistry is described. Emphasis is put on the chemical reactions and the importance of providing enantiopure synthons. In particular kinetics of resolution is in focus. Among the topics covered are enzyme classification, structure and mechanism of action of enzymes. Examples are given on the use of hydrolytic enzymes such as esterases, proteases, lipases, epoxide hydrolases, acylases and amidases both in aqueous and low-water media. Reductions and oxidations are treated both using whole cells and pure enzymes. Moreover, use of enzymes in sngar chemistiy and to prodnce amino acids and peptides are discnssed. 

Several cases are described (Cohen et ah, 1995) in which binding of an SH2-containing enzyme to an activated receptor tyrosine kinase leads to increased catalytic activity of the enzyme. Examples are the PI3-kinase and phospholipase Oy. The mechanism of activation is not clear. It is possible, however, that the basis is an allosteric mechanism, as is assumed for activation of Src tyrosine kinase. The Src kinase can be phosphoryla-... 

The packed-bed reactor configuration commonly employed with immobilized enzymes yields a higher degree of conversion or higher space-time yield than a CSTR, the typical configuration for soluble enzymes. Examples are the nitrile hydratase-catalyzed process to 5-cyanovaleramide (5-CVAM) (Chapter 7, Section 7.1.1.3) or the decarboxylation of D,L-aspartate to D-aspartate, L-alanine, and C02 (Section 7.2.2.5). 

Table 2 Inducible Human Drug Metabolizing Enzymes Examples of the Range of Variation of Expression Observed in Human Populations In Vivo or In Vitro... 

An irreversible inhibitor binds tightly, often covalently, to amino acid residues at the active site of the enzyme, permanently inactivating the enzyme. Examples of irreversible inhibitors are diisopropylfluorophosphate (DIPF), iodoacetamide and penicillin. 

Apolipoproteins serve to direct metabolism of particular lipoproteins by acting as cofactors or perhaps inhibitors for enzymes. Examples are apoA-I and apoC-I, each of which may activate lecithin cholesterol acyltransferase... 

The word to which the ending -ase has been added should preferably indicate the nature of the attached substrate (example, peptidase), or the mode of action of the enzyme (example, dehydrogenase), or a combination of the name of the substrate and the mode of action each time that it is necessary to avoid an ambiguity (example, succinyldehydro-genase). 

Many metabolic processes such as glycolysis, Krebs cycle reactions, photosynthesis, protein synthesis, and lipid metabolism are affected by exposure to F. Much of the action of F on these processes can be attributed to F-dependent inhibition of enzymes. Examples of enzymes shown to be inhibited by F include enolase, phosphoglucomutase, phosphatase, hexokinase, PEP carboxylase, pyruvate kinase, succinic dehydrogenase, malic dehydrogenase, pyrophosphatase, phytase, nitrate reductase, mitochondrial ATPase, urease (Miller et al. 1983), lipase (Yu et al. 1987), amylase (Yu et al. 1988), invertase (Yu 1996 Ouchi et al. 1999), and superoxide dismutase (SOD) (Wilde and Yu 1998). 

Activity stains are of great importance during the isolation, purification, and characterization of enzymes, since a particular catalytic reaction is involved and the detection of this activity leads to the unequivocal identification of the zone of interest on the electrophoresis gel. Following separation, the gel is removed from the electrophoresis apparatus and is immersed in a minimal volume of a substrate solution. Detection relies on the formation of a colored product by enzyme in the zones containing the enzyme. Examples of activity stains are given in Table 9.2. 

Second, it must be borne in mind that any observed increase in an enzyme activity or other feature in diseased muscle could result from a proliferation of nonmuscle tissue associated with the muscle. In particular, one must consider the possible contribution of metabolically active fat and connective tissue cells and the presence of invading macrophages. These are a characteristic feature of many kinds of diseased muscle and are rich in many enzymes. Examples are mentioned below... 

The two other multifunctional CaM kinase of types I and IV are, apart from Ca2+/ calmodulin control, regulated via phosphorylation by an upstream CaM kinase kinase, CaMKK (review Soderling, 1999). The CaMKKphosphorylates CaM kinase I and IV in the activation segment and thereby greatly enhances the activity of these enzymes. Examples of substrates of CaM kinases I and IV are transcription factors, the MAP kinases and adenylyl cyclase. 

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