Enzymes literature

Patient presents with elevated liver enzymes Literature... 

A much more ambitious database that builds on the IUBMB classification is BRENDA, maintained by the Institute of Biochemistry at the University of Cologne. In addition to the data provided by the ENZYME database, the BRENDA curators have extracted a large body of information from the enzyme literature and incorporated it into the database. The database format strives to be readable by both humans and machines. The categories of data stored in BRENDA comprise the EC-number, systematic and recommended names, synonyms, CAS-registry numbers, the reaction catalyzed, a list of known substrates and products, the natural substrates, specific activities, KM values, pH and temperature optima, cofactor and ion requirements, inhibitors, sources, localization, purification schemes, molecular weight, subunit structure, posttranslational modifications, enzyme stability, database links, and last but not least an extensive bibliography. Currently, BRENDA holds entries for approximately 3500 different enzymes. 

For example, incorporation of nickel into carbon monoxide dehydrogenase of Rhodospirillum rubrum requires the prior reduction of an Fe-S cluster. Structural studies of this protein reveal that the added Ni completes a unique [lNi-4Fe-4S] center that is required for activity.Another example of a reductive activation step occurs during NiFe-hydrogenase biosynthesis, perhaps involving participation of the Fe-S cluster in HypD. Yet a third example from the Ni-enzyme literature involves the synthesis of methyl-X-coenzyme M reductase, a methanogen enzyme that contains the Ni-tetrapyrrole cofactor F43q. Formation of active enzyme requires both the reduction of Ni + to NF+ and reduction of a C=N bond in the organic macrocycle. 

The concentrations of substances are indicated with lowercase letters, in accord with the nomenclature of the enzyme literature. Capital letters are used for quantities of materials (e.g., X = x V). 

Reaction, Rates. There are many embarrassing examples in the enzyme literature of errors in the assay method. These are generally avoided if it is ascertained that a rate of reaction is measured, and that this is proportional, to enzyme concentration. The rate of reaction may be linear with time, independent of the concentrations of substrates or products. Such reactions are termed zero order. If the reaction rate is proportional to the concentration of one substrate it is called first order (Mg. 2). These are... 

Because most soil enzyme studies deal with crude soil suspensions, or at best partially-purified soil extracts, care must be exercised in assigning an activity to the action of a particular enzyme. This note of caution is perhaps justified by considering the conversion in soils of urea to NH4 and CO2. Urea is an important nitrogenous fertilizer and is a major constituent of the urine of grazing animals, and studies of urea hydrolysis have dominated the soil enzyme literature. It is widely assumed that urea hydrolysis is catalysed by urease (urea amidohydrolase, EC 3.5.1.5). Studies have compared the kinetics and inhibition of urea hydrolysis by soils and by purified ureases, mainly from jack bean, Canavalia ensiformis, Jack bean urease catalyses urea hydrolysis by a pathway in which carbamate is an intermediate. 

There is quite a large body of literature on films of biological substances and related model compounds, much of it made possible by the sophisticated microscopic techniques discussed in Section IV-3E. There is considerable interest in biomembranes and how they can be modeled by lipid monolayers [35]. In this section we briefly discuss lipid monolayers, lipolytic enzyme reactions, and model systems for studies of biological recognition. The related subjects of membranes and vesicles are covered in the following section. 

Slow, tight-binding inhibition occurs when slow-binding inhibition takes place at inhibitor concentrations comparable to that of the enzyme, in which case the previous two mechanisms can still apply. Comprehensive review articles on the subject of tight, slow, and slow, tight-binding inhibitors ate available in the literature (12,14). 

The numerous separations reported in the literature include surfactants, inorganic ions, enzymes, other proteins, other organics, biological cells, and various other particles and substances. The scale of the systems ranges from the simple Grits test for the presence of surfactants in water, which has been shown to operate by virtue of transient foam fractionation [Lemlich, J. Colloid Interface Sci., 37, 497 (1971)], to the natural adsubble processes that occur on a grand scale in the ocean [Wallace and Duce, Deep Sea Res., 25, 827 (1978)]. For further information see the reviews cited earlier. 

This chapter lists some representative examples of biochemicals and their origins, a brief indication of key techniques used in their purification, and literature references where further details may be found. Simpler low molecular weight compounds, particularly those that may have been prepared by chemical syntheses, e.g. acetic acid, glycine, will be found in Chapter 4. Only a small number of enzymes and proteins are included because of space limitations. The purification of some of the ones that have been included has been described only briefly. The reader is referred to comprehensive texts such as the Methods Enzymol (Academic Press) series which currently runs to more than 344 volumes and The Enzymes (3rd Edn, Academic Press) which runs to 22 volumes for methods of preparation and purification of proteins and enzymes. Leading referenees on proteins will be found in Advances in Protein Chemistry (59 volumes. Academic Press) and on enzymes will be found in Advances in Enzymology (72 volumes, then became Advances in Enzymology and Related Area of Molecular Biology, J Wiley Sons). The Annual Review of Biochemistry (Annual Review Inc. Patio Alto California) also is an excellent source of key references to the up-to-date information on known and new natural compounds, from small molecules, e.g. enzyme cofactors to proteins and nucleic acids. 

Deprotection using enzymes can be quite useful. An added benefit is that a racemic or meso substrate can often be resolved with excellent enantio-selectivity. Numerous examples of this process are described in the literature. Although acetates are the most common substrates in enzymatic... 

Proteins have been hydrolyzed by treatment with sulfuric acid, hydrochloric acid, barium hydroxide, proteolytic enzymes, and other hydrolytic reagents, but no condition has been found which avoids some destruction or incomplete liberation of tryptophan, cystine, and some other amino acids. The early work on this problem has been reviewed by Mitchell and Hamilton (194). The literature and their own excellent experiments on the hydrolysis problem in relation to the liberation and destruction of tryptophan have been presented recently by Spies and Chambers (269). 

Other examples of concentrated laundry liquids have been described in the literature [53]. These might be called nonaqueous or low-water formulations. They may contain nonionic and anionic surfactants, inorganic builders, enzyme and bleach additives, and an organic solvent such as a low mole AE [54]. Surfactant levels may range from 30% up to 80%. In some cases, the builder salts are dispersed as solid particles in the non-aqueous phase [55]. 

In 1993, the di-D-fructose dianhydrides were summarized as being of little, if any, commercial importance. 73 However, a search of the literature reveals an appreciable number of patents issued since 1989 for the manufacture of these compounds. These include enzymic methods for the production of individual dianhydrides (Ref. 130) or methods of production of mixtures using anhydrous HF or pyridinium poly(hydrogen fluoride) (see Ref. 131). Most cite the di-D-fructose dianhydrides as low-calorie sweetening agents (Ref. 132), and some claim anti-cariogenic properties (Refs. 132 and 133). 

As shown in this chapter, by focusing on the modulation of enzyme selectivity by medium engineering, quite simple modifications of the solvent composition can really have significant effects on the performances of the biocatalysts. The main drawback remains the lack of reliable predictive models. Despite the significant research efforts (particularly in the last decade), it is likely that a reasonable foresight of the enantioselective outcome of an enzymatic transformation will continue to be based solely on a careful analysis of the increasingly numerous literature reports. 

These were relatively low-resolution structures, and with refinement some errors in the initial structural assignments have been detected (4-7). Since the structures were first reported the subject has been extensively reviewed in this series (8) and elsewhere 9-15). This review will focus on the structure, biosynthesis, and function of the met-allosulfur clusters found in nitrogenases. This will require a broader overview of some functional aspects, particularly the involvement of MgATP in the enzymic reaction, and also some reference will be made to the extensive literature (9, 15) on biomimetic chemistry that has helped to illuminate possible modes of nitrogenase function, although a detailed review of this chemistry will not be attempted here. This review cannot be fully comprehensive in the space available, but concentrates on recent advances and attempts to describe the current level of our understanding. 

QSAR modeling. Therefore considerably larger and more consistent data sets for each enzyme will be required in future to increase the predictive scope of such models. The evaluation of any rule-based metabolite software with a diverse array of molecules will indicate that it is possible to generate many more metabolites than have been identified in the literature for the respective molecules to date, which could also reflect the sensitivity of analytical methods at the time of publishing the data. In such cases, efficient machine learning algorithms will be necessary to indicate which of the metabolites are relevant and will be likely to be observed under the given experimental conditions. 

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