Sources of Enzymes

Lolis, E., and Petsko, G., 1990. Transition-state analogues in protein crystallography Probes of the structural source of enzyme catalysis. Annual Review of Biochemistry 59 597—630. 

In nature, there are several sources of enzymes that are capable of catalysing the hydrolysis of PHB. The polymer itself is produced by bacteria and occurs in cells as discrete inclusion bodies. These bodies contain the necessary enzymes for degrading the polymer, preventing its build-up in the cell. As well as this, there are numerous bacteria and fungi, many of which are found in the soil, that are capable of secreting the necessary enzymes outside their cell walls, and thus of iiufiating degradation of PHB. 

Sulfate reducing bacteria of the genus Desulfovibrio are one of the main sources of enzyme. Hydrogenases can be found in different sites in the bacterial cell periplasm, cytoplasm, and membrane. A given species may have hydrogenases in one or in several of these cell sites. 

Vertebrate liver is a very rich source of enzymes that metabolize lipophilic xenobiotics, and subcellular fractions are prepared to study metabolism. Sometimes, other tissues such as brain, kidney, testis, and ovary are also treated in this way. A typical subcellular fractionation of liver might be as follows ... 

All soil metabolic proce.sses are driven by enzymes. The main sources of enzymes in soil are roots, animals, and microorganisms the last are considered to be the most important (49). Once enzymes are produced and excreted from microbial cells or from root cells, they face harsh conditions most may be rapidly decomposed by organisms (50), part may be adsorbed onto soil organomineral colloids and possibly protected against microbial degradation (51), and a minor portion may stand active in soil solution (52). The fraction of extracellular enzyme activity of soil, which is not denaturated and/or inactivated through interactions with soil fabric (51), is called naturally stabilized or immobilized. Moreover, it has been hypothesized that immobilized enzymes have a peculiar behavior, for they might not require cofactors for their catalysis. 

Compared with isolated enzymes, enzymes used in whole-cell biotransformations are often more stable due to the presence of their natural environment inside the cell. This is especially true for the enzymes involved in the oxidation and hydroxylation reactions that are labile once isolated from the cells. They are a convenient and stable source of enzymes that are often synthesized by cells in response to the presence of the substrate. 

There are two sources of enzymes that are added to flour, neither of which count as improvers. 

Human liver microsomes (HLMs) are the most common in vitro sources of enzymes for inhibition studies, and selective probe substrates are required. Recombinant human P450 enzymes have become commercially available. They are widely used for screening, and less selective probe substrate can be used. Hepatocytes and liver slices48 have also been used for P450 inhibition screening to a lesser extent. 

Tapia, O. and Andres, J. On a quantum theory of chemical reactions and the role of in vacuum transition stmetures. Primary and secondary sources of enzyme catalysis, J.Mol.Str (THEOCHEM), 335 (1995), 267-286... 

Figure 7.15 Enzyme-multiplied immunoassay (EMIT). The three reactants, test (or standard) antigen, enzyme-labelled antigen and a limited amount of antibody are allowed to react and reach an equilibrium position. The unbound labelled antigen which remains is the only source of enzyme activity, the bound enzyme being inactivated. This free enzyme can be quantitated using a direct kinetic assay method and is proportional to the amount of unlabelled antigen originally present.

It is possible to bind enzymes to an insoluble matrix by a variety of methods and still retain their catalytic activity. The reusable nature of immobilized enzymes can significantly reduce costs and provides a convenient source of enzymes for performing substrate assays. Such preparations often show a greater stability and reduced inhibition effects than do soluble enzymes, although occasionally optimum pH values may be altered slightly. 

If measurements are made in a system containing a purified or a cloned and expressed enzyme, then assays are relatively straightforward if the species being measured is chemically stable under the reaction conditions. However, if tissue homogenates are used as a source of enzyme, the potential exists for the product of interest to be further metabolized by one or more contaminating enzymes, or even for the substrate to be subjected to an alternative metabolic process. This can be particularly problematic when the... 

The rapid progress in the understanding of the active site of aconitase in the 1980 s has primarily originated from the work of H. Beinert and his collaborators. Three essential factors contributed to the success of this work 1) a ready and consistent source of enzyme (gram quantities), 2) a solid chemical and biochemical understanding of aconitase, and 3) close interactions with outstanding collaborators (most notably E. Munck s group for Mossbauer spectroscopy and B. M. 

Source of Enzymes. Culture filtrates of T. reesei strains VTT-D-79125 and Rut C-30 were used as starting material for purification of the individual enzymes and also as crude enzyme preparations in the hydrolysis experiments. Cultivations were carried out in a laboratory fermentor at 30°C for 4d on media containing Solka floe cellulose (James River Corp., New Hampshire, USA), or glucose and distiller s spent grain (Alko, Ltd., Koskenkorva, Finland). 

An vitro enzyme system from onion was used to show that this pathway was operative in plants ( , ). Onion was chosen as the source of enzymes because pentachlorothioanlsole was an important metabolite of PCNB in onion ( ). 

Many microbial sources of enzymes suitable for converting them into L-phenylalanine... 

Source of Enzyme (s) E. coli B. brevis and Agrobacterium radiobacter B. cereus, Candida bodinii Cryptococcus laurentii and Achromobacter obae P. putid,... 

Source of Enzyme (s) Pig pancreas A. sclerotiorum S. cerevisiae Rhodococcus rhodochrous Achromobacter xylosooxydans... 

Glycoprotein or GP M.W. Source of enzyme 2-Acetamido-2-deoxy-D-glucose (moles/ mole of protein) Total Released Refer- ences... 

Sphingolipidosis OMIM numbers Enzyme deficiency/defective protein Source of enzyme for postnatal diagnosis Main glycosphingolipid storage products Sample for storage product analysis... 

For multicellular organisms, the tissue used for isolation of the enzyme or the tissue in which the enzyme is present is given. Cell-lines may also be a source of enzymes. 

The production of enzymes is the major (argei of numerous biological conversions. In years pasl, the principal sources of enzymes were extraction products from plant and animal sources. The application of DNA technology has made large inroads in ihe production of synihelic" enzymes. 

Source of enzyme" Molecular weight Molecular activity1 Sedimentation coefficient (1013 X 20,w) rUcm "280 (nm/mg N) Electrophoretic mobility" (cm2/sec/VX 10-6) Ref. 

Source of enzyme Phenoxy- methyl- pencillin Ampi- cillin Methi- cillin Oxa- cillin Cloxa- cillin 6-APA Cepha- losporin C Benzyl- cepha- losporin Cepha- loridine Ref. 

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